James Ellis

James Ellis

1573121091

HTTP requests using Axios

The most common way for frontend programs to communicate with servers is through the HTTP protocol. You are probably familiar with the Fetch API and the XMLHttpRequest interface, which allow you fetch resources and make HTTP requests.

If you are using a JavaScript library, chances are it comes with a client HTTP API. jQuery’s $.ajax() function, for example, has been particularly popular with frontend developers. But as developers move away from such libraries in favor of native APIs, dedicated HTTP clients have emerged to fill the gap.

In this post we will take a good look at Axios, a client HTTP API based on the XMLHttpRequest interface provided by browsers, and examine the key features that has contributed to its rise in popularity among frontend developers.

Why Axios?

As with Fetch, Axios is promise-based. However, it provides a more powerful and flexible feature set. Advantages over the native Fetch API include:

  • Request and response interception
  • Streamlined error handling
  • Protection against XSRF
  • Support for upload progress
  • Response timeout
  • The ability to cancel requests
  • Support for older browsers
  • Automatic JSON data transformation

Installation

You can install Axios using:

  • npm:
$ npm install axios
  • The Bower package manager:
$ bower install axios
  • Or a content delivery network:
<script src="https://unpkg.com/axios/dist/axios.min.js"></script>

Making requests

Making an HTTP request is as easy as passing a config object to the Axios function. In its simplest form, the object must have a url property; if no method is provided, GET will be used as the default value. Let’s look at a simple example:

// send a POST request
axios({
  method: 'post',
  url: '/login',
  data: {
    firstName: 'Finn',
    lastName: 'Williams'
  }
});

This should look familiar to those who have worked with jQuery’s $.ajax function. This code is simply instructing Axios to send a POST request to /login with an object of key/value pairs as its data. Axios will automatically convert the data to JSON and send it as the request body.

Shorthand methods

Axios also provides a set of shorthand methods for performing different types of requests. The methods are as follows:

  • axios.request(config)
  • axios.get(url[, config])
  • axios.delete(url[, config])
  • axios.head(url[, config])
  • axios.options(url[, config])
  • axios.post(url[, data[, config]])
  • axios.put(url[, data[, config]])
  • axios.patch(url[, data[, config]])

For instance, the following code shows how the previous example could be written using the axios.post() method:

axios.post('/login', {
  firstName: 'Finn',
  lastName: 'Williams'
});

Handling the response

Once an HTTP request is made, Axios returns a promise that is either fulfilled or rejected, depending on the response from the backend service. To handle the result, you can use the then() method like this:

axios.post('/login', {
  firstName: 'Finn',
  lastName: 'Williams'
})
.then((response) => {
  console.log(response);
}, (error) => {
  console.log(error);
});

If the promise is fulfilled, the first argument of then() will be called; if the promise is rejected, the second argument will be called. According to the documentation, the fulfillment value is an object containing the following information:

{
  // `data` is the response that was provided by the server
  data: {},
 
  // `status` is the HTTP status code from the server response
  status: 200,
 
  // `statusText` is the HTTP status message from the server response
  statusText: 'OK',
 
  // `headers` the headers that the server responded with
  // All header names are lower cased
  headers: {},
 
  // `config` is the config that was provided to `axios` for the request
  config: {},
 
  // `request` is the request that generated this response
  // It is the last ClientRequest instance in node.js (in redirects)
  // and an XMLHttpRequest instance the browser
  request: {}
}

As an example, here’s how the response looks when requesting data from the GitHub API:

axios.get('https://api.github.com/users/mapbox')
  .then((response) => {
    console.log(response.data);
    console.log(response.status);
    console.log(response.statusText);
    console.log(response.headers);
    console.log(response.config);
  });

// logs:
// => {login: "mapbox", id: 600935, node_id: "MDEyOk9yZ2FuaXphdGlvbjYwMDkzNQ==", avatar_url: "https://avatars1.githubusercontent.com/u/600935?v=4", gravatar_id: "", …}
// => 200
// => OK
// => {x-ratelimit-limit: "60", x-github-media-type: "github.v3", x-ratelimit-remaining: "60", last-modified: "Wed, 01 Aug 2018 02:50:03 GMT", etag: "W/"3062389570cc468e0b474db27046e8c9"", …}
// => {adapter: ƒ, transformRequest: {…}, transformResponse: {…}, timeout: 0, xsrfCookieName: "XSRF-TOKEN", …}

Making simultaneous requests

One of Axios’ more interesting features is its ability to make multiple requests in parallel by passing an array of arguments to the axios.all() method. This method returns a single promise object that resolves only when all arguments passed as an array have resolved. Here’s a simple example:

// execute simultaneous requests 
axios.all([
  axios.get('https://api.github.com/users/mapbox'),
  axios.get('https://api.github.com/users/phantomjs')
])
.then(responseArr => {
  //this will be executed only when all requests are complete
  console.log('Date created: ', responseArr[0].data.created_at);
  console.log('Date created: ', responseArr[1].data.created_at);
});

// logs:
// => Date created:  2011-02-04T19:02:13Z
// => Date created:  2017-04-03T17:25:46Z

This code makes two requests to the GitHub API and then logs the value of the created_at property of each response to the console. Keep in mind that if any of the arguments rejects then the promise will immediately reject with the reason of the first promise that rejects.

For convenience, Axios also provides a method called axios.spread() to assign the properties of the response array to separate variables. Here’s how you could use this method:

axios.all([
  axios.get('https://api.github.com/users/mapbox'),
  axios.get('https://api.github.com/users/phantomjs')
])
.then(axios.spread((user1, user2) => {
  console.log('Date created: ', user1.data.created_at);
  console.log('Date created: ', user2.data.created_at);
}));

// logs:
// => Date created:  2011-02-04T19:02:13Z
// => Date created:  2017-04-03T17:25:46Z

The output of this code is the same as the previous example. The only difference is that the axios.spread() method is used to unpack values from the response array.

Sending custom headers

Sending custom headers with Axios is very straightforward. Simply pass an object containing the headers as the last argument. For example:

const options = {
  headers: {'X-Custom-Header': 'value'}
};

axios.post('/save', { a: 10 }, options);

Transforming requests and responses

By default, Axios automatically converts requests and responses to JSON. But it also allows you to override the default behavior and define a different transformation mechanism. This ability is particularly useful when working with an API that accepts only a specific data format such as XML or CSV.

To change the request data before sending it to the server, set the transformRequest property in the config object. Note that this method only works for PUT, POST, and PATCH request methods. Here’s how you can do that:

const options = {
  method: 'post',
  url: '/login',
  data: {
    firstName: 'Finn',
    lastName: 'Williams'
  },
  transformRequest: [(data, headers) => {
    // transform the data

    return data;
  }]
};

// send the request
axios(options);

To modify the data before passing it to then() or catch(), you can set the transformResponse property:

const options = {
  method: 'post',
  url: '/login',
  data: {
    firstName: 'Finn',
    lastName: 'Williams'
  },
  transformResponse: [(data) => {
    // transform the response

    return data;
  }]
};

// send the request
axios(options);

Intercepting requests and responses

HTTP Interception is a popular feature of Axios. With this feature, you can examine and change HTTP requests from your program to the server and vice versa, which is very useful for a variety of implicit tasks, such as logging and authentication.

At first glance, interceptors look very much like transforms, but they differ in one key way: unlike transforms, which only receive the data and headers as arguments, interceptors receive the entire response object or request config.

You can declare a request interceptor in Axios like this:

// declare a request interceptor
axios.interceptors.request.use(config => {
  // perform a task before the request is sent
  console.log('Request was sent');

  return config;
}, error => {
  // handle the error
  return Promise.reject(error);
});

// sent a GET request
axios.get('https://api.github.com/users/mapbox')
  .then(response => {
    console.log(response.data.created_at);
  });

This code logs a message to the console whenever a request is sent then waits until it gets a response from the server, at which point it prints the time the account was created at GitHub to the console. One advantage of using interceptors is that you no longer have to implement tasks for each HTTP request separately.

Axios also provides a response interceptor, which allows you to transform the responses from a server on their way back to the application:

// declare a response interceptor
axios.interceptors.response.use((response) => {
  // do something with the response data
  console.log('Response was received');

  return response;
}, error => {
  // handle the response error
  return Promise.reject(error);
});

// sent a GET request
axios.get('https://api.github.com/users/mapbox')
  .then(response => {
    console.log(response.data.created_at);
  });

Client-side support for protection against XSRF

Cross-site request forgery (or XSRF for short) is a method of attacking a web-hosted app in which the attacker disguises himself as a legal and trusted user to influence the interaction between the app and the user’s browser. There are many ways to execute such an attack, including XMLHttpRequest.

Fortunately, Axios is designed to protect against XSRF by allowing you to embed additional authentication data when making requests. This enables the server to discover requests from unauthorized locations. Here’s how this can be done with Axios:

const options = {
  method: 'post',
  url: '/login',
  xsrfCookieName: 'XSRF-TOKEN',
  xsrfHeaderName: 'X-XSRF-TOKEN',
};

// send the request
axios(options);

While Axios has some features for debugging requests and responses, making sure Axios continues to serve resources to your app in production is where things get tougher. If you’re interested in ensuring requests to the backend or 3rd party services are successful, try LogRocket. [LogRocket Dashboard Free Trial Banner

This is image title

LogRocket is like a DVR for web apps, recording literally everything that happens on your site. Instead of guessing why problems happen, you can aggregate and report on problematic Axios requests to quickly understand the root cause.

LogRocket instruments your app to record baseline performance timings such as page load time, time to first byte, and slow network requests as well as logs Redux, NgRx. and Vuex actions/state. Start monitoring for free.

Monitoring POST request progress

Another interesting feature of Axios is the ability to monitor request progress. This is especially useful when downloading or uploading large files. The provided example in the Axios documentation gives you a good idea of how that can be done. But for the sake of simplicity and style, we are going to use the Axios Progress Bar module in this tutorial.

The first thing we need to do to use this module is to include the related style and script:

<link rel="stylesheet" type="text/css" href="https://cdn.rawgit.com/rikmms/progress-bar-4-axios/0a3acf92/dist/nprogress.css" />

<script src="https://cdn.rawgit.com/rikmms/progress-bar-4-axios/0a3acf92/dist/index.js"></script>

Then we can implement the progress bar like this:

loadProgressBar()

const url = 'https://media.giphy.com/media/C6JQPEUsZUyVq/giphy.gif';

function downloadFile(url) {
  axios.get(url)
  .then(response => {
    console.log(response)
  })
  .catch(error => {
    console.log(error)
  })
}

downloadFile(url);

To change the default styling of the progress bar, we can override the following style rules:

#nprogress .bar {
    background: red !important;
}

#nprogress .peg {
    box-shadow: 0 0 10px red, 0 0 5px red !important;
}

#nprogress .spinner-icon {
    border-top-color: red !important;
    border-left-color: red !important;
}

Canceling requests

In some situations, you may no longer care about the result and want to cancel a request that’s already sent. This can be done by using a cancel token. The ability to cancel requests was added to Axios in version 1.5 and is based on the cancelable promises proposal. Here’s a simple example:

const source = axios.CancelToken.source();

axios.get('https://media.giphy.com/media/C6JQPEUsZUyVq/giphy.gif', {
  cancelToken: source.token
}).catch(thrown => {
  if (axios.isCancel(thrown)) {
    console.log(thrown.message);
  } else {
    // handle error
  }
});

// cancel the request (the message parameter is optional)
source.cancel('Request canceled.');

You can also create a cancel token by passing an executor function to the CancelToken constructor, as shown below:

const CancelToken = axios.CancelToken;
let cancel;

axios.get('https://media.giphy.com/media/C6JQPEUsZUyVq/giphy.gif', {
  // specify a cancel token
  cancelToken: new CancelToken(c => {
    // this function will receive a cancel function as a parameter
    cancel = c;
  })
}).catch(thrown => {
  if (axios.isCancel(thrown)) {
    console.log(thrown.message);
  } else {
    // handle error
  }
});

// cancel the request
cancel('Request canceled.');

Libraries

Axios’ rise in popularity among developers has resulted in a rich selection of third-party libraries that extend its functionality. From testers to loggers, there’s a library for almost any additional feature you may need when using Axios. Here are some popular libraries currently available:

#Axios #programming #HTTP #HTTP requests

What is GEEK

Buddha Community

HTTP requests using Axios
Chloe  Butler

Chloe Butler

1667425440

Pdf2gerb: Perl Script Converts PDF Files to Gerber format

pdf2gerb

Perl script converts PDF files to Gerber format

Pdf2Gerb generates Gerber 274X photoplotting and Excellon drill files from PDFs of a PCB. Up to three PDFs are used: the top copper layer, the bottom copper layer (for 2-sided PCBs), and an optional silk screen layer. The PDFs can be created directly from any PDF drawing software, or a PDF print driver can be used to capture the Print output if the drawing software does not directly support output to PDF.

The general workflow is as follows:

  1. Design the PCB using your favorite CAD or drawing software.
  2. Print the top and bottom copper and top silk screen layers to a PDF file.
  3. Run Pdf2Gerb on the PDFs to create Gerber and Excellon files.
  4. Use a Gerber viewer to double-check the output against the original PCB design.
  5. Make adjustments as needed.
  6. Submit the files to a PCB manufacturer.

Please note that Pdf2Gerb does NOT perform DRC (Design Rule Checks), as these will vary according to individual PCB manufacturer conventions and capabilities. Also note that Pdf2Gerb is not perfect, so the output files must always be checked before submitting them. As of version 1.6, Pdf2Gerb supports most PCB elements, such as round and square pads, round holes, traces, SMD pads, ground planes, no-fill areas, and panelization. However, because it interprets the graphical output of a Print function, there are limitations in what it can recognize (or there may be bugs).

See docs/Pdf2Gerb.pdf for install/setup, config, usage, and other info.


pdf2gerb_cfg.pm

#Pdf2Gerb config settings:
#Put this file in same folder/directory as pdf2gerb.pl itself (global settings),
#or copy to another folder/directory with PDFs if you want PCB-specific settings.
#There is only one user of this file, so we don't need a custom package or namespace.
#NOTE: all constants defined in here will be added to main namespace.
#package pdf2gerb_cfg;

use strict; #trap undef vars (easier debug)
use warnings; #other useful info (easier debug)


##############################################################################################
#configurable settings:
#change values here instead of in main pfg2gerb.pl file

use constant WANT_COLORS => ($^O !~ m/Win/); #ANSI colors no worky on Windows? this must be set < first DebugPrint() call

#just a little warning; set realistic expectations:
#DebugPrint("${\(CYAN)}Pdf2Gerb.pl ${\(VERSION)}, $^O O/S\n${\(YELLOW)}${\(BOLD)}${\(ITALIC)}This is EXPERIMENTAL software.  \nGerber files MAY CONTAIN ERRORS.  Please CHECK them before fabrication!${\(RESET)}", 0); #if WANT_DEBUG

use constant METRIC => FALSE; #set to TRUE for metric units (only affect final numbers in output files, not internal arithmetic)
use constant APERTURE_LIMIT => 0; #34; #max #apertures to use; generate warnings if too many apertures are used (0 to not check)
use constant DRILL_FMT => '2.4'; #'2.3'; #'2.4' is the default for PCB fab; change to '2.3' for CNC

use constant WANT_DEBUG => 0; #10; #level of debug wanted; higher == more, lower == less, 0 == none
use constant GERBER_DEBUG => 0; #level of debug to include in Gerber file; DON'T USE FOR FABRICATION
use constant WANT_STREAMS => FALSE; #TRUE; #save decompressed streams to files (for debug)
use constant WANT_ALLINPUT => FALSE; #TRUE; #save entire input stream (for debug ONLY)

#DebugPrint(sprintf("${\(CYAN)}DEBUG: stdout %d, gerber %d, want streams? %d, all input? %d, O/S: $^O, Perl: $]${\(RESET)}\n", WANT_DEBUG, GERBER_DEBUG, WANT_STREAMS, WANT_ALLINPUT), 1);
#DebugPrint(sprintf("max int = %d, min int = %d\n", MAXINT, MININT), 1); 

#define standard trace and pad sizes to reduce scaling or PDF rendering errors:
#This avoids weird aperture settings and replaces them with more standardized values.
#(I'm not sure how photoplotters handle strange sizes).
#Fewer choices here gives more accurate mapping in the final Gerber files.
#units are in inches
use constant TOOL_SIZES => #add more as desired
(
#round or square pads (> 0) and drills (< 0):
    .010, -.001,  #tiny pads for SMD; dummy drill size (too small for practical use, but needed so StandardTool will use this entry)
    .031, -.014,  #used for vias
    .041, -.020,  #smallest non-filled plated hole
    .051, -.025,
    .056, -.029,  #useful for IC pins
    .070, -.033,
    .075, -.040,  #heavier leads
#    .090, -.043,  #NOTE: 600 dpi is not high enough resolution to reliably distinguish between .043" and .046", so choose 1 of the 2 here
    .100, -.046,
    .115, -.052,
    .130, -.061,
    .140, -.067,
    .150, -.079,
    .175, -.088,
    .190, -.093,
    .200, -.100,
    .220, -.110,
    .160, -.125,  #useful for mounting holes
#some additional pad sizes without holes (repeat a previous hole size if you just want the pad size):
    .090, -.040,  #want a .090 pad option, but use dummy hole size
    .065, -.040, #.065 x .065 rect pad
    .035, -.040, #.035 x .065 rect pad
#traces:
    .001,  #too thin for real traces; use only for board outlines
    .006,  #minimum real trace width; mainly used for text
    .008,  #mainly used for mid-sized text, not traces
    .010,  #minimum recommended trace width for low-current signals
    .012,
    .015,  #moderate low-voltage current
    .020,  #heavier trace for power, ground (even if a lighter one is adequate)
    .025,
    .030,  #heavy-current traces; be careful with these ones!
    .040,
    .050,
    .060,
    .080,
    .100,
    .120,
);
#Areas larger than the values below will be filled with parallel lines:
#This cuts down on the number of aperture sizes used.
#Set to 0 to always use an aperture or drill, regardless of size.
use constant { MAX_APERTURE => max((TOOL_SIZES)) + .004, MAX_DRILL => -min((TOOL_SIZES)) + .004 }; #max aperture and drill sizes (plus a little tolerance)
#DebugPrint(sprintf("using %d standard tool sizes: %s, max aper %.3f, max drill %.3f\n", scalar((TOOL_SIZES)), join(", ", (TOOL_SIZES)), MAX_APERTURE, MAX_DRILL), 1);

#NOTE: Compare the PDF to the original CAD file to check the accuracy of the PDF rendering and parsing!
#for example, the CAD software I used generated the following circles for holes:
#CAD hole size:   parsed PDF diameter:      error:
#  .014                .016                +.002
#  .020                .02267              +.00267
#  .025                .026                +.001
#  .029                .03167              +.00267
#  .033                .036                +.003
#  .040                .04267              +.00267
#This was usually ~ .002" - .003" too big compared to the hole as displayed in the CAD software.
#To compensate for PDF rendering errors (either during CAD Print function or PDF parsing logic), adjust the values below as needed.
#units are pixels; for example, a value of 2.4 at 600 dpi = .0004 inch, 2 at 600 dpi = .0033"
use constant
{
    HOLE_ADJUST => -0.004 * 600, #-2.6, #holes seemed to be slightly oversized (by .002" - .004"), so shrink them a little
    RNDPAD_ADJUST => -0.003 * 600, #-2, #-2.4, #round pads seemed to be slightly oversized, so shrink them a little
    SQRPAD_ADJUST => +0.001 * 600, #+.5, #square pads are sometimes too small by .00067, so bump them up a little
    RECTPAD_ADJUST => 0, #(pixels) rectangular pads seem to be okay? (not tested much)
    TRACE_ADJUST => 0, #(pixels) traces seemed to be okay?
    REDUCE_TOLERANCE => .001, #(inches) allow this much variation when reducing circles and rects
};

#Also, my CAD's Print function or the PDF print driver I used was a little off for circles, so define some additional adjustment values here:
#Values are added to X/Y coordinates; units are pixels; for example, a value of 1 at 600 dpi would be ~= .002 inch
use constant
{
    CIRCLE_ADJUST_MINX => 0,
    CIRCLE_ADJUST_MINY => -0.001 * 600, #-1, #circles were a little too high, so nudge them a little lower
    CIRCLE_ADJUST_MAXX => +0.001 * 600, #+1, #circles were a little too far to the left, so nudge them a little to the right
    CIRCLE_ADJUST_MAXY => 0,
    SUBST_CIRCLE_CLIPRECT => FALSE, #generate circle and substitute for clip rects (to compensate for the way some CAD software draws circles)
    WANT_CLIPRECT => TRUE, #FALSE, #AI doesn't need clip rect at all? should be on normally?
    RECT_COMPLETION => FALSE, #TRUE, #fill in 4th side of rect when 3 sides found
};

#allow .012 clearance around pads for solder mask:
#This value effectively adjusts pad sizes in the TOOL_SIZES list above (only for solder mask layers).
use constant SOLDER_MARGIN => +.012; #units are inches

#line join/cap styles:
use constant
{
    CAP_NONE => 0, #butt (none); line is exact length
    CAP_ROUND => 1, #round cap/join; line overhangs by a semi-circle at either end
    CAP_SQUARE => 2, #square cap/join; line overhangs by a half square on either end
    CAP_OVERRIDE => FALSE, #cap style overrides drawing logic
};
    
#number of elements in each shape type:
use constant
{
    RECT_SHAPELEN => 6, #x0, y0, x1, y1, count, "rect" (start, end corners)
    LINE_SHAPELEN => 6, #x0, y0, x1, y1, count, "line" (line seg)
    CURVE_SHAPELEN => 10, #xstart, ystart, x0, y0, x1, y1, xend, yend, count, "curve" (bezier 2 points)
    CIRCLE_SHAPELEN => 5, #x, y, 5, count, "circle" (center + radius)
};
#const my %SHAPELEN =
#Readonly my %SHAPELEN =>
our %SHAPELEN =
(
    rect => RECT_SHAPELEN,
    line => LINE_SHAPELEN,
    curve => CURVE_SHAPELEN,
    circle => CIRCLE_SHAPELEN,
);

#panelization:
#This will repeat the entire body the number of times indicated along the X or Y axes (files grow accordingly).
#Display elements that overhang PCB boundary can be squashed or left as-is (typically text or other silk screen markings).
#Set "overhangs" TRUE to allow overhangs, FALSE to truncate them.
#xpad and ypad allow margins to be added around outer edge of panelized PCB.
use constant PANELIZE => {'x' => 1, 'y' => 1, 'xpad' => 0, 'ypad' => 0, 'overhangs' => TRUE}; #number of times to repeat in X and Y directions

# Set this to 1 if you need TurboCAD support.
#$turboCAD = FALSE; #is this still needed as an option?

#CIRCAD pad generation uses an appropriate aperture, then moves it (stroke) "a little" - we use this to find pads and distinguish them from PCB holes. 
use constant PAD_STROKE => 0.3; #0.0005 * 600; #units are pixels
#convert very short traces to pads or holes:
use constant TRACE_MINLEN => .001; #units are inches
#use constant ALWAYS_XY => TRUE; #FALSE; #force XY even if X or Y doesn't change; NOTE: needs to be TRUE for all pads to show in FlatCAM and ViewPlot
use constant REMOVE_POLARITY => FALSE; #TRUE; #set to remove subtractive (negative) polarity; NOTE: must be FALSE for ground planes

#PDF uses "points", each point = 1/72 inch
#combined with a PDF scale factor of .12, this gives 600 dpi resolution (1/72 * .12 = 600 dpi)
use constant INCHES_PER_POINT => 1/72; #0.0138888889; #multiply point-size by this to get inches

# The precision used when computing a bezier curve. Higher numbers are more precise but slower (and generate larger files).
#$bezierPrecision = 100;
use constant BEZIER_PRECISION => 36; #100; #use const; reduced for faster rendering (mainly used for silk screen and thermal pads)

# Ground planes and silk screen or larger copper rectangles or circles are filled line-by-line using this resolution.
use constant FILL_WIDTH => .01; #fill at most 0.01 inch at a time

# The max number of characters to read into memory
use constant MAX_BYTES => 10 * M; #bumped up to 10 MB, use const

use constant DUP_DRILL1 => TRUE; #FALSE; #kludge: ViewPlot doesn't load drill files that are too small so duplicate first tool

my $runtime = time(); #Time::HiRes::gettimeofday(); #measure my execution time

print STDERR "Loaded config settings from '${\(__FILE__)}'.\n";
1; #last value must be truthful to indicate successful load


#############################################################################################
#junk/experiment:

#use Package::Constants;
#use Exporter qw(import); #https://perldoc.perl.org/Exporter.html

#my $caller = "pdf2gerb::";

#sub cfg
#{
#    my $proto = shift;
#    my $class = ref($proto) || $proto;
#    my $settings =
#    {
#        $WANT_DEBUG => 990, #10; #level of debug wanted; higher == more, lower == less, 0 == none
#    };
#    bless($settings, $class);
#    return $settings;
#}

#use constant HELLO => "hi there2"; #"main::HELLO" => "hi there";
#use constant GOODBYE => 14; #"main::GOODBYE" => 12;

#print STDERR "read cfg file\n";

#our @EXPORT_OK = Package::Constants->list(__PACKAGE__); #https://www.perlmonks.org/?node_id=1072691; NOTE: "_OK" skips short/common names

#print STDERR scalar(@EXPORT_OK) . " consts exported:\n";
#foreach(@EXPORT_OK) { print STDERR "$_\n"; }
#my $val = main::thing("xyz");
#print STDERR "caller gave me $val\n";
#foreach my $arg (@ARGV) { print STDERR "arg $arg\n"; }

Download Details:

Author: swannman
Source Code: https://github.com/swannman/pdf2gerb

License: GPL-3.0 license

#perl 

James Ellis

James Ellis

1573121091

HTTP requests using Axios

The most common way for frontend programs to communicate with servers is through the HTTP protocol. You are probably familiar with the Fetch API and the XMLHttpRequest interface, which allow you fetch resources and make HTTP requests.

If you are using a JavaScript library, chances are it comes with a client HTTP API. jQuery’s $.ajax() function, for example, has been particularly popular with frontend developers. But as developers move away from such libraries in favor of native APIs, dedicated HTTP clients have emerged to fill the gap.

In this post we will take a good look at Axios, a client HTTP API based on the XMLHttpRequest interface provided by browsers, and examine the key features that has contributed to its rise in popularity among frontend developers.

Why Axios?

As with Fetch, Axios is promise-based. However, it provides a more powerful and flexible feature set. Advantages over the native Fetch API include:

  • Request and response interception
  • Streamlined error handling
  • Protection against XSRF
  • Support for upload progress
  • Response timeout
  • The ability to cancel requests
  • Support for older browsers
  • Automatic JSON data transformation

Installation

You can install Axios using:

  • npm:
$ npm install axios
  • The Bower package manager:
$ bower install axios
  • Or a content delivery network:
<script src="https://unpkg.com/axios/dist/axios.min.js"></script>

Making requests

Making an HTTP request is as easy as passing a config object to the Axios function. In its simplest form, the object must have a url property; if no method is provided, GET will be used as the default value. Let’s look at a simple example:

// send a POST request
axios({
  method: 'post',
  url: '/login',
  data: {
    firstName: 'Finn',
    lastName: 'Williams'
  }
});

This should look familiar to those who have worked with jQuery’s $.ajax function. This code is simply instructing Axios to send a POST request to /login with an object of key/value pairs as its data. Axios will automatically convert the data to JSON and send it as the request body.

Shorthand methods

Axios also provides a set of shorthand methods for performing different types of requests. The methods are as follows:

  • axios.request(config)
  • axios.get(url[, config])
  • axios.delete(url[, config])
  • axios.head(url[, config])
  • axios.options(url[, config])
  • axios.post(url[, data[, config]])
  • axios.put(url[, data[, config]])
  • axios.patch(url[, data[, config]])

For instance, the following code shows how the previous example could be written using the axios.post() method:

axios.post('/login', {
  firstName: 'Finn',
  lastName: 'Williams'
});

Handling the response

Once an HTTP request is made, Axios returns a promise that is either fulfilled or rejected, depending on the response from the backend service. To handle the result, you can use the then() method like this:

axios.post('/login', {
  firstName: 'Finn',
  lastName: 'Williams'
})
.then((response) => {
  console.log(response);
}, (error) => {
  console.log(error);
});

If the promise is fulfilled, the first argument of then() will be called; if the promise is rejected, the second argument will be called. According to the documentation, the fulfillment value is an object containing the following information:

{
  // `data` is the response that was provided by the server
  data: {},
 
  // `status` is the HTTP status code from the server response
  status: 200,
 
  // `statusText` is the HTTP status message from the server response
  statusText: 'OK',
 
  // `headers` the headers that the server responded with
  // All header names are lower cased
  headers: {},
 
  // `config` is the config that was provided to `axios` for the request
  config: {},
 
  // `request` is the request that generated this response
  // It is the last ClientRequest instance in node.js (in redirects)
  // and an XMLHttpRequest instance the browser
  request: {}
}

As an example, here’s how the response looks when requesting data from the GitHub API:

axios.get('https://api.github.com/users/mapbox')
  .then((response) => {
    console.log(response.data);
    console.log(response.status);
    console.log(response.statusText);
    console.log(response.headers);
    console.log(response.config);
  });

// logs:
// => {login: "mapbox", id: 600935, node_id: "MDEyOk9yZ2FuaXphdGlvbjYwMDkzNQ==", avatar_url: "https://avatars1.githubusercontent.com/u/600935?v=4", gravatar_id: "", …}
// => 200
// => OK
// => {x-ratelimit-limit: "60", x-github-media-type: "github.v3", x-ratelimit-remaining: "60", last-modified: "Wed, 01 Aug 2018 02:50:03 GMT", etag: "W/"3062389570cc468e0b474db27046e8c9"", …}
// => {adapter: ƒ, transformRequest: {…}, transformResponse: {…}, timeout: 0, xsrfCookieName: "XSRF-TOKEN", …}

Making simultaneous requests

One of Axios’ more interesting features is its ability to make multiple requests in parallel by passing an array of arguments to the axios.all() method. This method returns a single promise object that resolves only when all arguments passed as an array have resolved. Here’s a simple example:

// execute simultaneous requests 
axios.all([
  axios.get('https://api.github.com/users/mapbox'),
  axios.get('https://api.github.com/users/phantomjs')
])
.then(responseArr => {
  //this will be executed only when all requests are complete
  console.log('Date created: ', responseArr[0].data.created_at);
  console.log('Date created: ', responseArr[1].data.created_at);
});

// logs:
// => Date created:  2011-02-04T19:02:13Z
// => Date created:  2017-04-03T17:25:46Z

This code makes two requests to the GitHub API and then logs the value of the created_at property of each response to the console. Keep in mind that if any of the arguments rejects then the promise will immediately reject with the reason of the first promise that rejects.

For convenience, Axios also provides a method called axios.spread() to assign the properties of the response array to separate variables. Here’s how you could use this method:

axios.all([
  axios.get('https://api.github.com/users/mapbox'),
  axios.get('https://api.github.com/users/phantomjs')
])
.then(axios.spread((user1, user2) => {
  console.log('Date created: ', user1.data.created_at);
  console.log('Date created: ', user2.data.created_at);
}));

// logs:
// => Date created:  2011-02-04T19:02:13Z
// => Date created:  2017-04-03T17:25:46Z

The output of this code is the same as the previous example. The only difference is that the axios.spread() method is used to unpack values from the response array.

Sending custom headers

Sending custom headers with Axios is very straightforward. Simply pass an object containing the headers as the last argument. For example:

const options = {
  headers: {'X-Custom-Header': 'value'}
};

axios.post('/save', { a: 10 }, options);

Transforming requests and responses

By default, Axios automatically converts requests and responses to JSON. But it also allows you to override the default behavior and define a different transformation mechanism. This ability is particularly useful when working with an API that accepts only a specific data format such as XML or CSV.

To change the request data before sending it to the server, set the transformRequest property in the config object. Note that this method only works for PUT, POST, and PATCH request methods. Here’s how you can do that:

const options = {
  method: 'post',
  url: '/login',
  data: {
    firstName: 'Finn',
    lastName: 'Williams'
  },
  transformRequest: [(data, headers) => {
    // transform the data

    return data;
  }]
};

// send the request
axios(options);

To modify the data before passing it to then() or catch(), you can set the transformResponse property:

const options = {
  method: 'post',
  url: '/login',
  data: {
    firstName: 'Finn',
    lastName: 'Williams'
  },
  transformResponse: [(data) => {
    // transform the response

    return data;
  }]
};

// send the request
axios(options);

Intercepting requests and responses

HTTP Interception is a popular feature of Axios. With this feature, you can examine and change HTTP requests from your program to the server and vice versa, which is very useful for a variety of implicit tasks, such as logging and authentication.

At first glance, interceptors look very much like transforms, but they differ in one key way: unlike transforms, which only receive the data and headers as arguments, interceptors receive the entire response object or request config.

You can declare a request interceptor in Axios like this:

// declare a request interceptor
axios.interceptors.request.use(config => {
  // perform a task before the request is sent
  console.log('Request was sent');

  return config;
}, error => {
  // handle the error
  return Promise.reject(error);
});

// sent a GET request
axios.get('https://api.github.com/users/mapbox')
  .then(response => {
    console.log(response.data.created_at);
  });

This code logs a message to the console whenever a request is sent then waits until it gets a response from the server, at which point it prints the time the account was created at GitHub to the console. One advantage of using interceptors is that you no longer have to implement tasks for each HTTP request separately.

Axios also provides a response interceptor, which allows you to transform the responses from a server on their way back to the application:

// declare a response interceptor
axios.interceptors.response.use((response) => {
  // do something with the response data
  console.log('Response was received');

  return response;
}, error => {
  // handle the response error
  return Promise.reject(error);
});

// sent a GET request
axios.get('https://api.github.com/users/mapbox')
  .then(response => {
    console.log(response.data.created_at);
  });

Client-side support for protection against XSRF

Cross-site request forgery (or XSRF for short) is a method of attacking a web-hosted app in which the attacker disguises himself as a legal and trusted user to influence the interaction between the app and the user’s browser. There are many ways to execute such an attack, including XMLHttpRequest.

Fortunately, Axios is designed to protect against XSRF by allowing you to embed additional authentication data when making requests. This enables the server to discover requests from unauthorized locations. Here’s how this can be done with Axios:

const options = {
  method: 'post',
  url: '/login',
  xsrfCookieName: 'XSRF-TOKEN',
  xsrfHeaderName: 'X-XSRF-TOKEN',
};

// send the request
axios(options);

While Axios has some features for debugging requests and responses, making sure Axios continues to serve resources to your app in production is where things get tougher. If you’re interested in ensuring requests to the backend or 3rd party services are successful, try LogRocket. [LogRocket Dashboard Free Trial Banner

This is image title

LogRocket is like a DVR for web apps, recording literally everything that happens on your site. Instead of guessing why problems happen, you can aggregate and report on problematic Axios requests to quickly understand the root cause.

LogRocket instruments your app to record baseline performance timings such as page load time, time to first byte, and slow network requests as well as logs Redux, NgRx. and Vuex actions/state. Start monitoring for free.

Monitoring POST request progress

Another interesting feature of Axios is the ability to monitor request progress. This is especially useful when downloading or uploading large files. The provided example in the Axios documentation gives you a good idea of how that can be done. But for the sake of simplicity and style, we are going to use the Axios Progress Bar module in this tutorial.

The first thing we need to do to use this module is to include the related style and script:

<link rel="stylesheet" type="text/css" href="https://cdn.rawgit.com/rikmms/progress-bar-4-axios/0a3acf92/dist/nprogress.css" />

<script src="https://cdn.rawgit.com/rikmms/progress-bar-4-axios/0a3acf92/dist/index.js"></script>

Then we can implement the progress bar like this:

loadProgressBar()

const url = 'https://media.giphy.com/media/C6JQPEUsZUyVq/giphy.gif';

function downloadFile(url) {
  axios.get(url)
  .then(response => {
    console.log(response)
  })
  .catch(error => {
    console.log(error)
  })
}

downloadFile(url);

To change the default styling of the progress bar, we can override the following style rules:

#nprogress .bar {
    background: red !important;
}

#nprogress .peg {
    box-shadow: 0 0 10px red, 0 0 5px red !important;
}

#nprogress .spinner-icon {
    border-top-color: red !important;
    border-left-color: red !important;
}

Canceling requests

In some situations, you may no longer care about the result and want to cancel a request that’s already sent. This can be done by using a cancel token. The ability to cancel requests was added to Axios in version 1.5 and is based on the cancelable promises proposal. Here’s a simple example:

const source = axios.CancelToken.source();

axios.get('https://media.giphy.com/media/C6JQPEUsZUyVq/giphy.gif', {
  cancelToken: source.token
}).catch(thrown => {
  if (axios.isCancel(thrown)) {
    console.log(thrown.message);
  } else {
    // handle error
  }
});

// cancel the request (the message parameter is optional)
source.cancel('Request canceled.');

You can also create a cancel token by passing an executor function to the CancelToken constructor, as shown below:

const CancelToken = axios.CancelToken;
let cancel;

axios.get('https://media.giphy.com/media/C6JQPEUsZUyVq/giphy.gif', {
  // specify a cancel token
  cancelToken: new CancelToken(c => {
    // this function will receive a cancel function as a parameter
    cancel = c;
  })
}).catch(thrown => {
  if (axios.isCancel(thrown)) {
    console.log(thrown.message);
  } else {
    // handle error
  }
});

// cancel the request
cancel('Request canceled.');

Libraries

Axios’ rise in popularity among developers has resulted in a rich selection of third-party libraries that extend its functionality. From testers to loggers, there’s a library for almost any additional feature you may need when using Axios. Here are some popular libraries currently available:

#Axios #programming #HTTP #HTTP requests

Why Use WordPress? What Can You Do With WordPress?

Can you use WordPress for anything other than blogging? To your surprise, yes. WordPress is more than just a blogging tool, and it has helped thousands of websites and web applications to thrive. The use of WordPress powers around 40% of online projects, and today in our blog, we would visit some amazing uses of WordPress other than blogging.
What Is The Use Of WordPress?

WordPress is the most popular website platform in the world. It is the first choice of businesses that want to set a feature-rich and dynamic Content Management System. So, if you ask what WordPress is used for, the answer is – everything. It is a super-flexible, feature-rich and secure platform that offers everything to build unique websites and applications. Let’s start knowing them:

1. Multiple Websites Under A Single Installation
WordPress Multisite allows you to develop multiple sites from a single WordPress installation. You can download WordPress and start building websites you want to launch under a single server. Literally speaking, you can handle hundreds of sites from one single dashboard, which now needs applause.
It is a highly efficient platform that allows you to easily run several websites under the same login credentials. One of the best things about WordPress is the themes it has to offer. You can simply download them and plugin for various sites and save space on sites without losing their speed.

2. WordPress Social Network
WordPress can be used for high-end projects such as Social Media Network. If you don’t have the money and patience to hire a coder and invest months in building a feature-rich social media site, go for WordPress. It is one of the most amazing uses of WordPress. Its stunning CMS is unbeatable. And you can build sites as good as Facebook or Reddit etc. It can just make the process a lot easier.
To set up a social media network, you would have to download a WordPress Plugin called BuddyPress. It would allow you to connect a community page with ease and would provide all the necessary features of a community or social media. It has direct messaging, activity stream, user groups, extended profiles, and so much more. You just have to download and configure it.
If BuddyPress doesn’t meet all your needs, don’t give up on your dreams. You can try out WP Symposium or PeepSo. There are also several themes you can use to build a social network.

3. Create A Forum For Your Brand’s Community
Communities are very important for your business. They help you stay in constant connection with your users and consumers. And allow you to turn them into a loyal customer base. Meanwhile, there are many good technologies that can be used for building a community page – the good old WordPress is still the best.
It is the best community development technology. If you want to build your online community, you need to consider all the amazing features you get with WordPress. Plugins such as BB Press is an open-source, template-driven PHP/ MySQL forum software. It is very simple and doesn’t hamper the experience of the website.
Other tools such as wpFoRo and Asgaros Forum are equally good for creating a community blog. They are lightweight tools that are easy to manage and integrate with your WordPress site easily. However, there is only one tiny problem; you need to have some technical knowledge to build a WordPress Community blog page.

4. Shortcodes
Since we gave you a problem in the previous section, we would also give you a perfect solution for it. You might not know to code, but you have shortcodes. Shortcodes help you execute functions without having to code. It is an easy way to build an amazing website, add new features, customize plugins easily. They are short lines of code, and rather than memorizing multiple lines; you can have zero technical knowledge and start building a feature-rich website or application.
There are also plugins like Shortcoder, Shortcodes Ultimate, and the Basics available on WordPress that can be used, and you would not even have to remember the shortcodes.

5. Build Online Stores
If you still think about why to use WordPress, use it to build an online store. You can start selling your goods online and start selling. It is an affordable technology that helps you build a feature-rich eCommerce store with WordPress.
WooCommerce is an extension of WordPress and is one of the most used eCommerce solutions. WooCommerce holds a 28% share of the global market and is one of the best ways to set up an online store. It allows you to build user-friendly and professional online stores and has thousands of free and paid extensions. Moreover as an open-source platform, and you don’t have to pay for the license.
Apart from WooCommerce, there are Easy Digital Downloads, iThemes Exchange, Shopify eCommerce plugin, and so much more available.

6. Security Features
WordPress takes security very seriously. It offers tons of external solutions that help you in safeguarding your WordPress site. While there is no way to ensure 100% security, it provides regular updates with security patches and provides several plugins to help with backups, two-factor authorization, and more.
By choosing hosting providers like WP Engine, you can improve the security of the website. It helps in threat detection, manage patching and updates, and internal security audits for the customers, and so much more.

Read More

#use of wordpress #use wordpress for business website #use wordpress for website #what is use of wordpress #why use wordpress #why use wordpress to build a website

6 Things About HTTP Request in Dart For Beginners

Introduction

If you are here and a beginner, that means you want to learn everything about making an API request using Dart in Flutter, then you are in the right place for the HTTP tutorial. So without wasting any time, let’s start with this flutter tutorial. We will cover the essential topics required to work with the HTTP request in Dart.

What is Rest API in Dart ?

rest api flow

Rest APIs are a way to fetch data from the internet in flutter or communicate the server from the app and get some essential information from your server to the app. This information can be regarding your app’s data, user’s data, or any data you want to share globally from your app to all of your users.

This HTTP request fetches in a unique JSON format, and then the information is fetched from the JSON and put in the UI of the app.

Every programming language has a way of some internet connectivity i.e, use this rest API developed on the server and fetch data from the internet. To use this request feature, we have to add HTTP package in flutter, add this flutter package add in your project to use the http feature. Add this HTTP package to your pubspec.yaml, and run a command in terminal :

flutter packages get

#dart #flutter #async await #async function #cancel http api request in flutter #fetch data from the internet #flutter cancel future #flutter get request example #flutter post request example #future of flutter #http tutorial

Eliseo  Kutch

Eliseo Kutch

1625086260

React JS Tutorial - 12 - HTTP GET Request using Axios

In this video, we will learn about how to make http get request using Axios package.

#axios #react js #react #http