Open Source For You — December 2017

http://www.OpenSourceForU.com | OPEN SOURCE FOR YOU | DECEMBER 2017 | 73

Insight Developers

I

n the previous issue of OSFY, we tackled pattern matching

in PHP using regular expressions. PHP is most often used

as a server-side scripting language but what if your client

doesn’t want to bother the server with all the work? Well,

then you have to process regular expressions at the client side

with JavaScript, which is almost synonymous with client-side

scripting language. So, in this article, we’ll discuss regular

expressions in JavaScript.

Though, technically, JavaScript is a general-purpose

programming language, it is often used as a client-side

scripting language to create interactive Web pages. With

the help of JavaScript runtime environments like Node.js,

JavaScript can also be used at the server-side. However, in

this article, we will discuss only the client-side scripting

aspects of JavaScript because we have already discussed

regular expressions in the server-side scripting language—

PHP. Just like we found out about PHP in the previous article

in this series, you will mostly see JavaScript code embedded

inside HTML script. As mentioned earlier in the series,

limited knowledge of HTML syntax will in no way affect the

understanding of the regular expressions used in JavaScript.

Each programming language has its own way of parsing regular expressions. We have

looked at how regular expressions work with different languages in the earlier four articles

in this series. Now we explore regular expressions in JavaScript.

Though we are mostly interested in the use of regular

expressions, as always, let’s begin with a brief discussion on

the syntax and history of JavaScript.

JavaScript is an interpreted programming language.

ECMAScript is a scripting language specification from the

European Computer Manufacturer’s Association (ECMA)

and International Organization for Standardization (ISO),

standardised in ECMA-262 and ISO/IEC 16262 for

JavaScript. JavaScript was introduced by Netscape Navigator

(now defunct) in 1995; soon Microsoft followed with its own

version of JavaScript which was officially named JScript.

The first edition of ECMAScript was released in June 1997

in an effort to settle the disputes between Netscape and

Microsoft regarding the standardisation of JavaScript. The

latest edition of ECMAScript, version 8, was released in June

2017. All modern Web browsers support JavaScript with the
      help of a JavaScript engine that is based on the ECMAScript
      specification. Chrome V8, often known as V8, is an open
      source JavaScript engine developed by Google for the
      Chrome browser. Even though JavaScript has borrowed a lot
      of syntax from Java, do remember that JavaScript is not Java.

Regular Expressions in Programming

Languages: The JavaScript Story