How To Master Async/Await With This Real World Example

How To Master Async/Await With This Real World Example

Along with writing this article, I have also created a YouTube video! 

Originally published by Adrian Hajdin  at freecodecamp.org

Table of Contents:

  1. Introduction (callbacks, promises, async/await)
  2. Real world example — Currency Converter that is receiving asynchronous data from two API’s.

Just a note…

Along with writing this article, I have also created a YouTube video! 

You can follow along and code while watching. I advise you to first read the article, and then code along with the video.

Link of the video: Learn Async/Await in This Real World Project

Introduction

Async/await is a new way to write asynchronous code. It is built on top of promises, therefore, it is also non blocking.


The big difference is that asynchronous code looks and behaves a little more like synchronous code. This is where all its power lies.

Previous options for asynchronous code were callbacks and promises.

Callbacks in action

setTimeout(() => {
  console.log('This runs after 1000 milliseconds.');
}, 1000);

Problem with callbacks — The infamous Callback Hell

Nesting callbacks within callbacks will soon start to look like this:

Callback Hell

The situation where callbacks are nested within other callbacks several levels deep, potentially making it difficult to understand and maintain the code.

Promises in action

const promiseFunction = new Promise((resolve, reject) => {
  const add = (a, b) => a + b;
  resolve(add(2, 2));
});
promiseFunction.then((response) => {
  console.log(response);
}).catch((error) => {
  console.log(error);
});

promiseFunction returns a Promise that represents the process of that function. The resolve function signals the Promise instance that it has finished.

Afterwards, we can call .then() and .catch() on that promise function: 

then — Runs a callback you pass to it when the promise has finished.

catch — Runs a callback you pass to it when something went wrong.

Async Functions

Async function provide us with a clean and concise syntax that enables us to write less code to accomplish the same outcome we would get with promises. Async is nothing more than syntactic sugar for promises.


Async functions are created by prepending the word async before the function declaration like this:

const asyncFunction = async () => {
  // Code
}

Asynchronous functions can be paused with awaitthe keyword that can only be used inside an async function. Await returns whatever the async function returns when it is done.

This is the difference between promises and async/await:

// Async/Await
const asyncGreeting = async () => 'Greetings';
// Promises
const promiseGreeting = () => new Promise(((resolve) => {
  resolve('Greetings');
}));
asyncGreeting().then(result => console.log(result));
promiseGreeting().then(result => console.log(result));


Async/Await looks similar to synchronous code, and synchronous code is much easier to understand.

Now that we’ve covered the basics, let’s move onto our real world example!

Currency Converter

Project clarification and setup

In this tutorial, we will build a simple but educational and useful application that is going to improve your overall knowledge of Async/Await.


The program will take in currency code we want to convert from and currency code we want to convert to, as well as the amount of money. Afterwards, the program will output the correct exchange rate based on the data from the APIs.

In this application we’re going receive data from two asynchronous sources:

  1. Currency Layer — https://currencylayer.com — You’ll need to sign up for free so you can use the API Access Key. This API will provide us with data needed to calculate exchange rate between currencies.
  2. Rest Countries — http://restcountries.eu/ — This API will give us information about where can we use the currency we just converted our money to.

For starters, create a new directory and run npm init, skip through all the steps, and install axios by typing npm i --save axios. Create a new file called currency-converter.js.

Firstly, require axios by typing: const axios = require(‘axios’);

Let’s dive into async/await

Our goal for this program is to have three functions. Not one, not two, but three asynchronous functions. The first function is going to fetch data about currencies. The second function if going to fetch data about countries. And the third function is going to gather that information into one single place and output it nicely to the user.


First function — Receiving Currency Data Asynchronously

We’ll create an asynchronous function that is going to take in two arguments, fromCurrency and toCurrency.


const getExchangeRate = async (fromCurrency, toCurrency) => {}

Now we need to fetch the data. With async/await, we can assign data directly to a variable; don’t forget to sign up and enter your own correct access key.

const getExchangeRate = async (fromCurrency, toCurrency) => {
  const response = await axios.get('http://data.fixer.io/api/latest?    access_key=[yourAccessKey]&format=1');
}

The data from the response is available under response.data.rates so we can put that into a variable just below response:

const rate = response.data.rates;

Since everything is being converted from the euro, below, we’ll create a variable called euro which will be equal to 1/currency we want to convert from:

const euro = 1 / rate[fromCurrency];

Finally, to get an exchange rate we can multiply euros by the currency we want to convert to:

const exchangeRate = euro * rate[toCurrency];

Finally, the function should look something like this:

Second function — Receiving Country Data Asynchronously

We’ll create an asynchronous function that is going to take currencyCode as an argument:


const getCountries = async (currencyCode) => {}

As we saw before, we are going to fetch data and assign it to a variable:

const response = await axios.get(`https://restcountries.eu/rest/v2/currency/${currencyCode}`);

We’ll then map over the data and return country.name for each:

return response.data.map(country => country.name);

Finally, the function should look something like this:

Third and final function — Merging it all together

We’ll create an asynchronous function that is going to take fromCurrencytoCurrency, and amount as arguments:


const convert = async (fromCurrency, toCurrency, amount) => {}

First, we get the currency data:

const exchangeRate = await getExchangeRate(fromCurrency, toCurrency);

Second, we get the countries data:

const countries = await getCountries(toCurrency);

Third, we save the converted amount to a variable:

const convertedAmount = (amount * exchangeRate).toFixed(2);

Finally, we output it all to the user:

return `${amount} ${fromCurrency} is worth ${convertedAmount} ${toCurrency}. You can spend these in the following countries: ${countries}`;

All of that put together should look like this:

Adding try/catch to deal with error cases

We need to wrap all our logic in try, and catch the error if there is one:


const getExchangeRate = async (fromCurrency, toCurrency) => {
  try {
    const response = await       axios.get('http://data.fixer.io/api/latest?access_key=f68b13604ac8e570a00f7d8fe7f25e1b&format=1');
    const rate = response.data.rates;
    const euro = 1 / rate[fromCurrency];
    const exchangeRate = euro * rate[toCurrency];
    return exchangeRate;
  } catch (error) {
    throw new Error(`Unable to get currency ${fromCurrency} and  ${toCurrency}`);
  }
};

Repeat the same for the second function:

const getCountries = async (currencyCode) => {
  try {
    const response = await axios.get(`https://restcountries.eu/rest/v2/currency/${currencyCode}`);
return response.data.map(country => country.name);
  } catch (error) {
    throw new Error(`Unable to get countries that use ${currencyCode}`);
  }
};

And since the third function is just working with what the first and the second function provided, there is no need for error checking there.

Finally, we can call the function and receive the data:

convertCurrency('USD', 'HRK', 20)
  .then((message) => {
    console.log(message);
  }).catch((error) => {
    console.log(error.message);
  });

The output you’re going to receive:

That’s it!

You made it all the way until the end! If you get stuck along the way, feel free to check out the code on this repository. If you have any questions or feedback, let me know in the comments down below. Most helpful would be the support on YouTube since I have just created a channel! Click here, there is a lot of interesting stuff coming soon! :)


You can also check out the tutorial I did on Mongoose.


Originally published by Adrian Hajdin  at freecodecamp.org

===========================================

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JavaScript Tutorial: if-else Statement in JavaScript

JavaScript Tutorial: if-else Statement in JavaScript

This JavaScript tutorial is a step by step guide on JavaScript If Else Statements. Learn how to use If Else in javascript and also JavaScript If Else Statements. if-else Statement in JavaScript. JavaScript's conditional statements: if; if-else; nested-if; if-else-if. These statements allow you to control the flow of your program's execution based upon conditions known only during run time.

Decision Making in programming is similar to decision making in real life. In programming also we face some situations where we want a certain block of code to be executed when some condition is fulfilled.
A programming language uses control statements to control the flow of execution of the program based on certain conditions. These are used to cause the flow of execution to advance and branch based on changes to the state of a program.

JavaScript’s conditional statements:

  • if
  • if-else
  • nested-if
  • if-else-if

These statements allow you to control the flow of your program’s execution based upon conditions known only during run time.

  • if: if statement is the most simple decision making statement. It is used to decide whether a certain statement or block of statements will be executed or not i.e if a certain condition is true then a block of statement is executed otherwise not.
    Syntax:
if(condition) 
{
   // Statements to execute if
   // condition is true
}

Here, condition after evaluation will be either true or false. if statement accepts boolean values – if the value is true then it will execute the block of statements under it.
If we do not provide the curly braces ‘{‘ and ‘}’ after if( condition ) then by default if statement will consider the immediate one statement to be inside its block. For example,

if(condition)
   statement1;
   statement2;

// Here if the condition is true, if block 
// will consider only statement1 to be inside 
// its block.

Flow chart:

Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate If statement 

var i = 10; 

if (i > 15) 
document.write("10 is less than 15"); 

// This statement will be executed 
// as if considers one statement by default 
document.write("I am Not in if"); 

< /script> 

Output:

I am Not in if
  • if-else: The if statement alone tells us that if a condition is true it will execute a block of statements and if the condition is false it won’t. But what if we want to do something else if the condition is false. Here comes the else statement. We can use the else statement with if statement to execute a block of code when the condition is false.
    Syntax:
if (condition)
{
    // Executes this block if
    // condition is true
}
else
{
    // Executes this block if
    // condition is false
}


Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate If-else statement 

var i = 10; 

if (i < 15) 
document.write("10 is less than 15"); 
else
document.write("I am Not in if"); 

< /script> 

Output:

i is smaller than 15
  • nested-if A nested if is an if statement that is the target of another if or else. Nested if statements means an if statement inside an if statement. Yes, JavaScript allows us to nest if statements within if statements. i.e, we can place an if statement inside another if statement.
    Syntax:
if (condition1) 
{
   // Executes when condition1 is true
   if (condition2) 
   {
      // Executes when condition2 is true
   }
}

Example:

<script type = "text/javaScript"> 

// JavaScript program to illustrate nested-if statement 

var i = 10; 

if (i == 10) { 

// First if statement 
if (i < 15) 
	document.write("i is smaller than 15"); 

// Nested - if statement 
// Will only be executed if statement above 
// it is true 
if (i < 12) 
	document.write("i is smaller than 12 too"); 
else
	document.write("i is greater than 15"); 
} 
< /script> 

Output:

i is smaller than 15
i is smaller than 12 too
  • if-else-if ladder Here, a user can decide among multiple options.The if statements are executed from the top down. As soon as one of the conditions controlling the if is true, the statement associated with that if is executed, and the rest of the ladder is bypassed. If none of the conditions is true, then the final else statement will be executed.
if (condition)
    statement;
else if (condition)
    statement;
.
.
else
    statement;


Example:

<script type = "text/javaScript"> 
// JavaScript program to illustrate nested-if statement 

var i = 20; 

if (i == 10) 
document.wrte("i is 10"); 
else if (i == 15) 
document.wrte("i is 15"); 
else if (i == 20) 
document.wrte("i is 20"); 
else
document.wrte("i is not present"); 
< /script> 

Output:

i is 20

How to Retrieve full Profile of LinkedIn User using Javascript

How to Retrieve full Profile of LinkedIn User using Javascript

I am trying to retrieve the full profile (especially job history and educational qualifications) of a linkedin user via the Javascript (Fetch LinkedIn Data Using JavaScript)

Here we are fetching LinkedIn data like Username, Email and other fields using JavaScript SDK.

Here we have 2 workarounds.

  1. Configuration of linkedIn developer api
  2. Javascript Code to fetch records

Configuration of linkedIn developer api

In order to fetch records, first we need to create developer api in linkedin which will act as token/identity while fetching data from other linkedin accounts.

So to create api, navigate to https://linkedin.com/developer/apps and click on 'Create Application'.

After navigating, fill in details like name, description and other required fields and then submit.

As we submit, it will create Client ID and Client Secret shown below, which we will be using in our code while communicating to fetch records from other LinkedIn account.

Note: We need to provide localhost Url here under Oauth 2.0. I am using my localhost, but you can probably use other production URLs under Oauth 2.0 where your app is configured. It will make your api  consider the Url as trusted which fetching records.

Javascript Code to fetch records

For getting user details like first name, last name,User image can be written as,

<script type="text/javascript" src="https://platform.linkedin.com/in.js">  
    api_key: XXXXXXX //Client ID  
    onLoad: OnLinkedInFrameworkLoad //Method that will be called on page load  
    authorize: true  
</script>  
<script type="text/javascript">  
    function OnLinkedInFrameworkLoad() {  
        IN.Event.on(IN, "auth", OnLinkedInAuth);  
    }  
  
    function OnLinkedInAuth() {  
        IN.API.Profile("me").result(ShowProfileData);  
    }  
  
    function ShowProfileData(profiles) {  
        var member = profiles.values[0];  
        var id = member.id;  
        var firstName = member.firstName;  
        var lastName = member.lastName;  
        var photo = member.pictureUrl;  
        var headline = member.headline;  
        //use information captured above  
        var stringToBind = "<p>First Name: " + firstName + " <p/><p> Last Name: " + lastName + "<p/><p>User ID: " + id + " and Head Line Provided: " + headline + "<p/>"  
        document.getElementById('profiles').innerHTML = stringToBind;  
    }  
</script>    

Kindly note we need to include 'https://platform.linkedin.com/in.js' as src under script type as it will act on this Javascript SDK provided by Linkedin.

In the same way we can also fetch records of any organization with the companyid as keyword.

<head>  
    <script type="text/javascript" src="https://platform.linkedin.com/in.js">  
        api_key: XXXXXXX ////Client ID  
        onLoad: onLinkedInLoad  
        authorize: true  
    </script>  
</head>  
  
<body>  
    <div id="displayUpdates"></div>  
    <script type="text/javascript">  
        function onLinkedInLoad() {  
            IN.Event.on(IN, "auth", onLinkedInAuth);  
            console.log("On auth");  
        }  
  
        function onLinkedInAuth() {  
            var cpnyID = XXXXX; //the Company ID for which we want updates  
            IN.API.Raw("/companies/" + cpnyID + "/updates?event-type=status-update&start=0&count=10&format=json").result(displayCompanyUpdates);  
            console.log("After auth");  
        }  
  
        function displayCompanyUpdates(result) {  
            var div = document.getElementById("displayUpdates");  
            var el = "<ul>";  
            var resValues = result.values;  
            for (var i in resValues) {  
                var share = resValues[i].updateContent.companyStatusUpdate.share;  
                var isContent = share.content;  
                var isTitled = isContent,  
                    isLinked = isContent,  
                    isDescription = isContent,  
                    isThumbnail = isContent,  
                    isComment = isContent;  
                if (isTitled) {  
                    var title = isContent.title;  
                } else {  
                    var title = "News headline";  
                }  
                var comment = share.comment;  
                if (isLinked) {  
                    var link = isContent.shortenedUrl;  
                } else {  
                    var link = "#";  
                }  
                if (isDescription) {  
                    var description = isContent.description;  
                } else {  
                    var description = "No description";  
                }  
                /* 
                if (isThumbnailz) { 
                var thumbnailUrl = isContent.thumbnailUrl; 
                } else { 
                var thumbnailUrl = "http://placehold.it/60x60"; 
                } 
                */  
                if (share) {  
                    var content = "<a target='_blank' href=" + link + ">" + comment + "</a><br>";  
                    //el += "<li><img src='" + thumbnailUrl + "' alt=''>" + content + "</li>";  
                    el += "<li><div>" + content + "</div></li>";  
                }  
                console.log(share);  
            }  
            el += "</ul>";  
            document.getElementById("displayUpdates").innerHTML = el;  
        }  
    </script>  
</body>  

We can get multiple metadata while fetching records for any any organization. We can get company updates as shown below.

Conclusion

We can also fetch any company specific data like company job updates/post, total likes, comments, and number of views along with a lot of metadata we can fetch which I have shown below.

Thank you for reading !

7 Best Javascript Iframe Libraries

7 Best Javascript Iframe Libraries

Iframes let you build user experiences into embeddable ‘cross-domain components’, which let users interact with other sites without being redirected. I have compiled 7 best Javascript iframe libraries.

Iframes let you build user experiences into embeddable ‘cross-domain components’, which let users interact with other sites without being redirected. I have compiled 7 best Javascript iframe libraries.

1. Zoid

A cross-domain component toolkit, supporting:

  • Render an iframe or popup on a different domain, and pass down props, including objects and functions
  • Call callbacks natively from the child window without worrying about post-messaging or cross-domain restrictions
  • Create and expose components to share functionality from your site to others!
  • Render your component directly as a React, Vue or Angular component!
    It's 'data-down, actions up' style components, but 100% cross-domain using iframes and popups!

Download


2. Postmate

Postmate is a promise-based API built on postMessage. It allows a parent page to speak with a child iFrame across origins with minimal effort.

Download


3. Iframe Resizer

Keep same and cross domain iFrames sized to their content with support for window/content resizing, in page links, nesting and multiple iFrames

Demo

Download


4. Iframely

Embed proxy. Supports over 1800 domains via custom parsers, oEmbed, Twitter Cards and Open Graph

Demo

Download


5. React Frame component

This component allows you to encapsulate your entire React application or per component in an iFrame.

Demo

Download


6. Seamless.js

A seamless iframe makes it so that visitors are unable to distinguish between content within the iframe and content beside the iframe. Seamless.js is a JavaScript library (with no dependencies) that makes working with iframes easy by doing all the seamless stuff for you automatically.

Demo

Download


7. Porthole

A proxy to safely communicate to cross-domain iframes in javascript

Demo

Download


Thank for read!