Node.js by Example: Regular Expressions

JavaScript offers built-in support for regular expressions. Here are some examples of common regexp-related tasks.

There are two ways to create a Regular Expression object:

The Literal notation takes a pattern between two slashes, followed by optional flags, after the second slash.

 
const a = /p([a-z]+)ch/g;

The constructor function takes either a string or an existing RegExp object, the flags are the second parameter.

 
const b = new RegExp("p([a-z]+)ch", "i");
const c = new RegExp(/p([a-z]+)ch/, "i");

In JavaScript these are all equivalent. To test against a string we can call .test().

 
console.log(a.test("peach"));

Using a regular expression to change data format in a string.

 
const re = /(\w+)\s(\w+)/;
const str = "Maria Cruz";
const newStr = str.replace(re, "$2, $1");
console.log(newStr);

Splitting lines with different line endings.

 
const text =
  "Some text\nAnd some more\r\nAnd yet\nThis is the end";
const lines = text.split(/\r?\n/);
console.log(lines); 

$ node regular-expressions.js
true
Cruz, Maria
[
  'Some text',
  'And some more',
  'And yet',
  'This is the end'
]

Next example: .

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