O'Reilly logo

Learning JavaScript by Shelley Powers

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Chapter 2. JavaScript Data Types and Variables

The best part of JavaScript is that it’s forgiving, especially in regards to data typing. If you start out with a string and then want to use it as a number, that’s perfectly fine with the language. (Well, as long as the string actually contains a number and not something like an email address.) If you later want to treat it as a string again, that’s fine, too.

One could also say that the forgiving nature of JavaScript is one of the worst aspects of the language. If you try to add two numbers together, but the JavaScript engine interprets the variable holding one of them as a string data type, you end up with an odd string, rather than the sum you were expecting.

Context is everything when it comes to JavaScript data typing, and also when it comes to working with the most basic of JavaScript elements: the variable.

This chapter covers the three basic JavaScript data types: string, boolean, and number. Along the way, we’ll explore escape sequences in strings and take a brief look at Unicode. The chapter also delves into the topic of variables, including variable scope and what makes valid and meaningful variable identifiers. We’ll also look at the influences on identifiers that originate from the newest generation of JavaScript applications based on Ajax.

Identifying Variables

JavaScript variables have an identifier, scope, and a specific data type. Because the language is loosely typed, the rest, as they say, is subject to change without ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required