Book Image

Object-Oriented JavaScript - Third Edition

By : Ved Antani, Stoyan STEFANOV
5 (1)
Book Image

Object-Oriented JavaScript - Third Edition

5 (1)
By: Ved Antani, Stoyan STEFANOV

Overview of this book

JavaScript is an object-oriented programming language that is used for website development. Web pages developed today currently follow a paradigm that has three clearly distinguishable parts: content (HTML), presentation (CSS), and behavior (JavaScript). JavaScript is one important pillar in this paradigm, and is responsible for the running of the web pages. This book will take your JavaScript skills to a new level of sophistication and get you prepared for your journey through professional web development. Updated for ES6, this book covers everything you will need to unleash the power of object-oriented programming in JavaScript while building professional web applications. The book begins with the basics of object-oriented programming in JavaScript and then gradually progresses to cover functions, objects, and prototypes, and how these concepts can be used to make your programs cleaner, more maintainable, faster, and compatible with other programs/libraries. By the end of the book, you will have learned how to incorporate object-oriented programming in your web development workflow to build professional JavaScript applications.
Table of Contents (25 chapters)
Object-Oriented JavaScript - Third Edition
About the Authors
About the Reviewer
Customer Feedback
Built-in Functions
Regular Expressions

Block scope

ES6 provides additional scope while declaring variables. We looked at function scope and how it affects variables declared with the var keyword. If you are coding in ES6, block scope will mostly replace your need to use variables declared using var. Although, if you are still with ES5, we want you to make sure that you look at hoisting behavior carefully.

ES6 introduces the let and const keywords that allow us to declare variables.

Variables declared with let are block-scoped. They exist only within the current block. Variables declared with var are function scoped, as we saw earlier. The following example illustrates the block scope:

    var a = 1; 
        let a = 2; 
        console.log( a );   // 2 
    console.log( a );       // 1 

The scope between an opening brace'{' and a closing brace '}' is a block. If you are coming from a background in Java or C/C++, the concept of a block scope will be very familiar to you. In those languages...