Web/JavaScript/Reference/Global objects/String/startsWith

The startsWith() method determines whether a string begins with the characters of a specified string, returning true or false as appropriate.

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Syntax

str.startsWith(searchString[, position])

Parameters

searchString: The characters to be searched for at the start of this string.
position Optional: The position in this string at which to begin searching for searchString. Defaults to 0.

Return value

true if the given characters are found at the beginning of the string; otherwise, false.

Description

This method lets you determine whether or not a string begins with another string. This method is case-sensitive.

Examples

Using startsWith()

//startswith
let str = 'To be, or not to be, that is the question.'

console.log(str.startsWith('To be'))          // true
console.log(str.startsWith('not to be'))      // false
console.log(str.startsWith('not to be', 10))  // true

Polyfill

This method has been added to the ECMAScript 2015 specification and may not be available in all JavaScript implementations yet. However, you can polyfill String.prototype.startsWith() with the following snippet:

if (!String.prototype.startsWith) {
    Object.defineProperty(String.prototype, 'startsWith', {
        value: function(search, rawPos) {
            var pos = rawPos > 0 ? rawPos|0 : 0;
            return this.substring(pos, pos + search.length) === search;
        }
    });
}

A more robust (fully ES2015 specification compliant), but less performant and compact, Polyfill is available on GitHub by Mathias Bynens.

Specifications

Specification
ECMAScript (ECMA-262)The definition of 'String.prototype.startsWith' in that specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`startsWith`	Chrome Full support 41	Edge Full support 12	Firefox Full support 17	IE No support No	Opera Full support 28	Safari Full support 9	WebView Android Full support ≤37	Chrome Android Full support 36	Firefox Android Full support 17	Opera Android Full support 24	Safari iOS Full support 9	Samsung Internet Android Full support 3.0	nodejs Full support 4.0.0 Full support 4.0.0 Full support 0.12 Disabled' Disabled' From version 0.12: this feature is behind the `--harmony` runtime flag.

Legend

Full support: Full support
No support: No support
User must explicitly enable this feature.': User must explicitly enable this feature.