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

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.

Description

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

Examples

Using startsWith()

//startswith
var 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 6 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) {
    String.prototype.startsWith = function(searchString, position){
      position = position || 0;
      return this.substr(position, searchString.length) === searchString;
  };
}

A more robust and optimized Polyfill is available on GitHub by Mathias Bynens.

Specifications

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'String.prototype.startsWith' in that specification.
Standard Initial definition.
ECMAScript 2017 Draft (ECMA-262)
The definition of 'String.prototype.startsWith' in that specification.
Draft  

Browser compatibility

Feature Chrome Firefox (Gecko) Edge Internet Explorer Opera Safari
Basic support 41 17 (17) (Yes) No support 28 9
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support 36 17.0 (17) No support No support No support

 

Please note that although the MSDN documentation for this method (https://msdn.microsoft.com/en-us/library/mt146831(v=vs.94).aspx) clearly indicates that it is not supported in Internet Explorer, the method does seem to work, as far back as Internet Explorer 8.

See also