endsWith in JavaScript

UPDATE (Nov 24th, 2015):

This answer is originally posted in the year 2010 (SIX years back.) so please take note of these insightful comments:

  • Shauna –

Update for Googlers – Looks like ECMA6 adds this function. The MDN article also shows a polyfill. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/endsWith

  • T.J. Crowder –

Creating substrings isn’t expensive on modern browsers; it may well have been in 2010 when this answer was posted. These days, the simple this.substr(-suffix.length) === suffix approach is fastest on Chrome, the same on IE11 as indexOf, and only 4% slower (fergetaboutit territory) on Firefox: https://jsben.ch/OJzlM And faster across the board when the result is false: jsperf.com/endswith-stackoverflow-when-false Of course, with ES6 adding endsWith, the point is moot. 🙂


I know this is a year old question… but I need this too and I need it to work cross-browser so… combining everyone’s answer and comments and simplifying it a bit:

String.prototype.endsWith = function(suffix) {
    return this.indexOf(suffix, this.length - suffix.length) !== -1;
  • Doesn’t create a substring
  • Uses native indexOf function for fastest results
  • Skip unnecessary comparisons using the second parameter of indexOf to skip ahead
  • Works in Internet Explorer
  • NO Regex complications

Also, if you don’t like stuffing things in native data structure’s prototypes, here’s a standalone version:

function endsWith(str, suffix) {
    return str.indexOf(suffix, str.length - suffix.length) !== -1;

EDIT: As noted by @hamish in the comments, if you want to err on the safe side and check if an implementation has already been provided, you can just adds a typeof check like so:

if (typeof String.prototype.endsWith !== 'function') {
    String.prototype.endsWith = function(suffix) {
        return this.indexOf(suffix, this.length - suffix.length) !== -1;

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