Async/await in JavaScript : asynchronous behaviour of Javascript Part -4

For part 1, part 2 and part 3 of this series, see the following links https://truetocode.com/understanding-callbacks-and-callback-hell-in-javascript-asynchronous-behavior-of-javascript-part-1/697/ https://truetocode.com/understanding-promises-in-javascript-asynchronous-behavior-of-javascript-part-2/730/ https://truetocode.com/generator-functions-in-javascript-asynchronous-behavior-of-javascript-part-3/744/ In the previous three articles in this series, we learned about doing asynchronous operations with callbacks, promises, and generator functions. In ES8 or ES2017 , Javascript introduced a new kind of syntax called async/await, which makes it easier to do asynchronous operations. Async/await syntax is actually just syntactic sugar over promises and callbacks The following example shows the basic syntax for performing async/await operations. Here too, we use fetch function which returns a promise. Remember that this block of code is run on chrome 60. Earlier versions of Chrome do not support async/ await. fetch()  and  json() returns promise

Now using async/await

Both will produce output like  the following The fetch() here returns a promise so we await for fetch. The json() function also returns a promise so we await for that too. Here we can see that using the async/await made the code easier to read and understand. As you can see that async/await helps you to write code in a way that asynchronous code looks and behave a  more like synchronous code. On each await keyword, the function pauses as you can see in the below…

Understanding Callbacks and Callback hell in JavaScript : asynchronous behaviour of Javascript Part -1

In most programming languages, functions can accept other function(s) as arguments or return a function. Such functions are called Higher-order functions. In JavaScript, most APIs and Modules can accept a function as an argument to a function. The functions are called callbacks. Structure of callbacks

Note that JavaScript functions behave as objects. We can set a function as an object property or store a function into a variable. JavaScript is a non-blocking programming language. It doesn’t wait or block operation to finish but keeps on executing. For example, consider the case when data is fetched asynchronously, then javascript doesn’t wait for the asynchronous call to get data but keeps executing the next line of code. So in order to do something with the data, we can use callbacks. See the below example in which we use a timeout to wait for the data just like an XHR request which may take some time to complete

Asynchronous callback with  Jquery and a callback function

  CALLBACK HELL Consider the above example in which we use a callback function which is passed as an argument to the $.get function in Jquery. Now what happens when we want to send subsequent requests is that…

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