Book Image

Learn ECMAScript - Second Edition

By : MEHUL MOHAN, Narayan Prusty
Book Image

Learn ECMAScript - Second Edition

By: MEHUL MOHAN, Narayan Prusty

Overview of this book

Learn ECMAScript explores implementation of the latest ECMAScript features to add to your developer toolbox, helping you to progress to an advanced level. Learn to add 1 to a variable andsafely access shared memory data within multiple threads to avoid race conditions. You’ll start the book by building on your existing knowledge of JavaScript, covering performing arithmetic operations, using arrow functions and dealing with closures. Next, you will grasp the most commonly used ECMAScript skills such as reflection, proxies, and classes. Furthermore, you’ll learn modularizing the JS code base, implementing JS on the web and how the modern HTML5 + JS APIs provide power to developers on the web. Finally, you will learn the deeper parts of the language, which include making JavaScript multithreaded with dedicated and shared web workers, memory management, shared memory, and atomics. It doesn’t end here; this book is 100% compatible with ES.Next. By the end of this book, you'll have fully mastered all the features of ECMAScript!
Table of Contents (18 chapters)
Title Page
PacktPub.com
Contributors
Preface
Index

Generator function


A generator is a normal function, but instead of returning a single value, it returns multiple values one by one. Calling a generator function doesn't execute its body immediately, but rather returns a new instance of the generator object (that is, an object that implements both, iterable and iterator protocols).

Every generator object holds a new execution context of the generator function. When we execute the next() method of the generator object, it executes the generator function's body until the yield keyword is encountered. It returns the yielded value and pauses the function. When the next() method is called again, it resumes the execution and then returns the next yielded value. The done property is true when the generator function doesn't yield any value.

A generator function is written using the function* expression. Here is an example to demonstrate this:

function* generator_function(){ 
  yield 1; 
  yield 2; 
  yield 3;
  yield 4; 
  yield 5;
}
let generator...