string.startsWith

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.

Return value

true if the string begins with the characters of the search 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
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 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) {
    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

See also

• String.prototype.endsWith()
• String.prototype.includes()
• String.prototype.indexOf()
• String.prototype.lastIndexOf()