String.prototype.trimStart()

The trimStart() method removes whitespace from the beginning of a string. trimLeft() is an alias of this method.

Syntax

trimStart()

trimLeft()

Return value

A new string representing str stripped of whitespace from its beginning (left side).

If the beginning of str has no whitespace, a new string is still returned (essentially a copy of str), with no exception being thrown.

Aliasing

For consistency with functions like String.prototype.padStart the standard method name is trimStart. However, for web compatibility reasons, trimLeft remains as an alias to trimStart. In some engines this means:

String.prototype.trimLeft.name === "trimStart";

Examples

Using trimStart()

The following example displays the lowercase string 'foo ':

var str = '   foo  ';

console.log(str.length); // 8

str = str.trimStart();
console.log(str.length); // 5
console.log(str);        // 'foo  '

Polyfill

//https://github.com/FabioVergani/js-Polyfill_String-trimStart

(function(w){
    var String=w.String, Proto=String.prototype;

    (function(o,p){
        if(p in o?o[p]?false:true:true){
            var r=/^\s+/;
            o[p]=o.trimLeft||function(){
                return this.replace(r,'')
            }
        }
    })(Proto,'trimStart');

})(window);

/*
ES6:
(w=>{
    const String=w.String, Proto=String.prototype;

    ((o,p)=>{
        if(p in o?o[p]?false:true:true){
            const r=/^\s+/;
            o[p]=o.trimLeft||function(){
                return this.replace(r,'')
            }
        }
    })(Proto,'trimStart');

})(window);
*/

Specifications

Specification
ECMAScript Language Specification (ECMAScript) # sec-string.prototype.trimstart

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`trimStart`	66 4	79 12	61 3.5	No	53 15	12	66 ≤37	66 18	61 4	47 14	12	9.0 1.0