Steve Griffith

Steve Griffith

1623860683

Converting Callback Functions to Promises

https://www.youtube.com/watch?v=DxWqsNMccHY

Learn how to turn callbacks into Promises that you can reuse in projects.

#es6 #promises #javascript #web-development

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Buddha Community

Converting Callback Functions to Promises
Vincent Lab

Vincent Lab

1605017502

The Difference Between Regular Functions and Arrow Functions in JavaScript

Other then the syntactical differences. The main difference is the way the this keyword behaves? In an arrow function, the this keyword remains the same throughout the life-cycle of the function and is always bound to the value of this in the closest non-arrow parent function. Arrow functions can never be constructor functions so they can never be invoked with the new keyword. And they can never have duplicate named parameters like a regular function not using strict mode.

Here are a few code examples to show you some of the differences
this.name = "Bob";

const person = {
name: “Jon”,

<span style="color: #008000">// Regular function</span>
func1: <span style="color: #0000ff">function</span> () {
    console.log(<span style="color: #0000ff">this</span>);
},

<span style="color: #008000">// Arrow function</span>
func2: () =&gt; {
    console.log(<span style="color: #0000ff">this</span>);
}

}

person.func1(); // Call the Regular function
// Output: {name:“Jon”, func1:[Function: func1], func2:[Function: func2]}

person.func2(); // Call the Arrow function
// Output: {name:“Bob”}

The new keyword with an arrow function
const person = (name) => console.log("Your name is " + name);
const bob = new person("Bob");
// Uncaught TypeError: person is not a constructor

If you want to see a visual presentation on the differences, then you can see the video below:

#arrow functions #javascript #regular functions #arrow functions vs normal functions #difference between functions and arrow functions

Jeromy  Lowe

Jeromy Lowe

1595553079

Intro to Callback in JavaScript

During my journey of learning JavaScript and a few days in with React, I had to come to terms with callback functions. It was impossible to avoid its existence and blindly using it without understanding. To understand callback function we have to know a bit about functions. Here I want to talk about function expression, arrow function, and callback function.


What is a Callback function?

According to MDN doc:

A callback function is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action.

In JavaScript, functions are objects, which means, like any other objects it can be assigned to a variable and passed as an argument to another function. In a nutshell, a callback function is a function that is provided as a parameter for other methods such as forEach method or addEventListener method and gets invoked at a certain point in time.

Passing functions as arguments

So how do we do this? Let’s see with an example below:

document.addEventListener(‘click’,whoAmI);

//whoAmI Function Declaration(Function Statement)
function whoAmI(event){
  console.log(event.target.tagName)
}

We attached the ‘click’ event listener to document with whoAmI function as a parameter that logs the tag name of the clicked target. Whenever ‘click’ happens whoAmI function will be called with an _event_ argument. We call whoAmI a callback function.

When we call a function by its name followed by ( ), we are telling the function to execute its code. When we name a function or pass a function without the ( ), the function does not execute.** The callback function doesn’t execute right away. Instead, the addEventListener method executes the function when the event occurs.**

One more thing I want to mention is because we used function declaration, we were able to call thewhoAmI function before it was declared. It’s the magic of hoisting in JS. But with function expression, it doesn’t get hoisted. So the order of writing function expressions and using them as callback would be crucial.

#callback #javascript #callback-function #function #javascript-fundamental

Hugo JS

Hugo JS

1599295469

What is Callback-Function in JavaScript? How it is Replaced By Promises?

Let us understand term _Callback _by an real-world example: Suppose, you are calling to your Girlfriend (If you have) and she is busy in another call then she send message to you : “I am busy right now, Call back you later.!!”. After completing her work, she calls you back and this is what call back in JavaScript as well.

In JavaScript, When a function is executing (Girlfriend is talking with someone) then after function execution is completed another function is started for execution this is call back function.

Now you are thinking that its depend upon when, where you are calling function and all function call is “Call-back function”. Image for post

Here, _printWorld() _function is executed after _printHello() _complete its execution but this is not call-back function example because _printHello() _is not Asynchronous function. Suppose, _printHello() _prints after 1 Second then _printWorld() _executes first.

Image for post

What if we want “Hello World” output when Asynchronous function is there. We can pass function as argument and calls it after _printHello() _complete its execution. Here below code snippet of how _function pass as argument _:

Image for post

Callback function can be defined as a function passed by argument and executes when one function completes its execution.

Suppose, If you have API (Application Programming Interface) to get Students Roll numbers and select one of Roll number — getting that roll number’s data and print that data. We don’t have API to get students data so we are using _setTimeout() _Async function and getting roll number after 2s, We are also selecting one of roll number manually after 2s and print Roll number’s data after 2s. This can be done by call back function.

Image for post

The program became complex and complex if we have too many things to do like Getting Students data, Selecting one of them student, get student’s roll number and get result by roll number then it become very complex. If you have any Error in this then debugging is also tedious task, this things is called “Callback Hell”, which is shape like “Pyramid Of Doom”.

To overcome with this problem, Promises is introduced in JavaScript. Promises has three states : Pending, Resolved, Reject. Promises is created by Constructor : new Promise(). It has one executor function which has two arguments (resolve, reject).

Promise object has three methods: then(), catch() & finally().

Image for post

If Promise is successfully executed then its data is transferred through resolve function and if it has error then passed through reject function.

We have implemented same task which is done using call back function in Promises and its easily understandable However it is complicated compare to callback function but when you use promises for sometimes then it’s easy to implement.

In _getRollNumber(), _resolve method’s data is caught by then() functions arguments and reject method’s data is caught by catch() function. Here In Promises, Every task has different promises because of that it is easy to debug and readable compare to call back function. You can see that there is no shape like “Pyramid of Doom” in Promises. This is how Callback function is replaced by Promises.

Thank you for reading!

This article was originally published on Medium.com

#javascript-tips #advanced-javascript #javascript #callback-function #promises

Rajat Rajput

1625301328

OST to PST Converter Free to Convert OST to PST Online

When the exchange server is synchronised with MS Outlook then, automatically a copy of its mailboxes will be generated in OST (Offline Storage Table) file format. The user can access OST data in the offline mode and work on them. The changes will get updated when the internet connectivity is re-established. OST files cannot be accessed in the other system or remote system. So to access the OST files in another system Outlook, then convert Outlook OST to PST format. Due to various reasons for which users’ want to convert OST to PST file format such as the Exchange might face some technical issues, downtime or crash. How to convert OST to PST in Outlook 2016, 2013, 2010? Well, in this blog, we will discuss both manual as well as the professional best OST to PST Converter online solution.
For better understanding of users’, we have listed some common reasons below.

Why There is a Need to Export OST to PST Outlook?

Before providing methods to the query “how to convert OST file to PST in outlook 2016”, first understand why users’ need to convert OST to PST. Some of the basic reasons are provided below.

  • When the Exchange server is under maintenance.
  • Accidental deletion of the Exchange server account.
  • Virus or Malware attacks.
  • Power Failures or intrusions by malicious software.

These are a few reasons for Outlook OST to PST conversion. Now let’s proceed ahead to different methods to convert OST to PST online.

How to Convert OST to PST in Outlook 2016 Manually?

Manual strategies are cost-effective methods and here, we will discuss the complete manual steps for OST to PST conversion. Before starting the steps, it is suggested to create a backup copy of the original data as there might be a risk of human error that can ultimately lead to severe data loss. How to convert OST to PST manually? Follow the methods provided below -

Method 1: Import/ Export Feature

  1. Open your Microsoft Outlook program.
  2. Click on the File tab.
  3. Select the Import/Export option.
  4. Click on Export to a file.
  5. Press the Next button.
  6. Now Select the Personal File folder (.pst).
  7. Click on the Parent root.
  8. Check on the include subfolders
  9. Click on browse and navigate to the path to save the resultant data.
  10. Click on the finish button.

Method 2: Use Outlook Archive Feature

  1. Sign-in to Microsoft Outlook.
  2. Go to the File section
  3. Click on Options
  4. Now, click on the Advanced section
  5. Click on Auto Archive settings…
  6. Navigate to the path to save the archived files.
  7. Click on the OK button.

Drawbacks

  • Manual Processes are lengthy and more time-consuming.
  • Need connectivity with the Exchange server.
  • Unable to export corrupt OST data.
  • Outlook application installation is required.
  • Feasible for small sized OST files only.
  • High risk of data loss.

How to Convert OST to PST in Outlook 2016 Using DRS OST to PST Converter

To avoid all the limitations that we have already seen above with the conventional manual techniques, users can opt for a well known and reliable automated method for conversion. There are numerous third-party solutions available to convert OST to PST, however it is suggested to use a trusted software. Using the smart DRS Best OST to PST Converter online utility that allows to export OST to PST, MBOX, MSG, EML, PDF, CSV, HTML, Gmail, Yandex mail, Yahoo, Office 365, etc. It can easily open corrupt OST files and convert them to healthy PST. The tool even allows users to smoothly export all the mailbox items like attachments, calendar, contacts, journals, tasks, etc. There are no file size restrictions and no risk of severe data loss. The advanced software is compatible with all versions of Mac and Windows. The free OST to PST Converter online version allows to export 50 emails for free.

Conclusion

Above in this blog, we have discussed the recommended solutions by experts on the query “how to convert OST to PST in Outlook 2016”. At the end of this article, we can conclude that manual strategies have several limitations, so it is suggested to use the well known DRS OST to PST Converter for an effective, accurate and effortless conversion.

#how to convert ost file to pst in outlook 2016 #how to convert ost to pst online #how to convert ost to pst manually #convert ost to pst #ost to pst converter #outlook ost to pst

Promise.allSettled() vs Promise.all()

Promise.allSetlled() is recently introduced in ECMA 2020.
Check out how it is different from Promise.all()

https://www.geekstutorialpoint.com/2020/05/promiseallsettled-vs-promiseall.html

#javascript #promise.all #promise.allsettled #ecma #promise #jquery