JavaScript - String trim() method example

In this short article, we are going to discuss how to trim strings in JavaScript.

There are 3 different ways to trim string:

• both sides - most commonly used
• left side
• right side

Quick overlook:

// ONLINE-RUNNER:browser;

var text = '    abc    ';

// Both side trimming:
console.log(     'abc' === text.trim()                    ); // true
console.log(     'abc' === text.replace(/^\s*|\s*$/g, '') ); // true

// Left side trimming:
console.log( 'abc    ' === text.replace(/^\s*/g, '') ); // true

// Right side trimming:
console.log( '    abc' === text.replace(/\s*$/g, '') ); // true

Left and right side trimming with ECMAScript 2020:

// ONLINE-RUNNER:browser;

var text = '    abc    ';

// left side trimming:
console.log( 'abc    ' === text.trimStart() ); // true
console.log( 'abc    ' === text.trimLeft()  ); // true

// right side trimming:
console.log( '    abc' === text.trimEnd()   ); // true
console.log( '    abc' === text.trimRight() ); // true

 Note: trimStart, trimLeft, trimEnd, trimRight are in draft of ECMAScript 2020, so it is better to use replace approach until the methods will be commonly supported.

More detailed and grouped substring methods description is placed below.

1. Documentation

2. Trim operation with built-in methods example

In this section, two ways how to trim strings in javascript are represented. One of them is based on String trim method. The second one replaces white characters with regular expressions.

// ONLINE-RUNNER:browser;

var text = '    abc    ';

console.log( 'abc' === text.trim()                    ); // true
console.log( 'abc' === text.replace(/^\s*|\s*$/g, '') ); // true

3. Side trimming operation with built-in methods example

JavaScript API provides additionally left and right trimming.

3.1. Left side trimming

// ONLINE-RUNNER:browser;

var text = '    abc    ';

console.log( 'abc    ' === text.replace(/^\s*/g, '') ); // true
console.log( 'abc    ' === text.trimStart()          ); // true
console.log( 'abc    ' === text.trimLeft()           ); // true

Note: trimStart and trimLeft are in draft of ECMAScript 2020, so it is better to use replace approach until the methods will be commonly supported.

3.2. Right side trimming

// ONLINE-RUNNER:browser;

var text = '    abc    ';

console.log( '    abc' === text.replace(/\s*$/g, '') ); // true
console.log( '    abc' === text.trimEnd()            ); // true
console.log( '    abc' === text.trimRight()          ); // true

Note: trimEnd and trimRight are in draft of ECMAScript 2020, so it is better to use replace approach until the methods will be commonly supported.