endsWith in JavaScript – Dev

The best answers to the question “endsWith in JavaScript” in the category Dev.

QUESTION:

How can I check if a string ends with a particular character in JavaScript?

Example: I have a string

var str = "mystring#";

I want to know if that string is ending with #. How can I check it?

  1. Is there a endsWith() method in JavaScript?

  2. One solution I have is take the length of the string and get the last character and check it.

Is this the best way or there is any other way?

ANSWER:

/#$/.test(str)

will work on all browsers, doesn’t require monkey patching String, and doesn’t require scanning the entire string as lastIndexOf does when there is no match.

If you want to match a constant string that might contain regular expression special characters, such as '$', then you can use the following:

function makeSuffixRegExp(suffix, caseInsensitive) {
  return new RegExp(
      String(suffix).replace(/[$%()*+.?\[\\\]{|}]/g, "\\$&") + "$",
      caseInsensitive ? "i" : "");
}

and then you can use it like this

makeSuffixRegExp("a[complicated]*suffix*").test(str)

ANSWER:

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: jsperf.com/endswith-stackoverflow/14 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. 🙂


ORIGINAL ANSWER:

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;
    };
}

ANSWER:

Come on, this is the correct endsWith implementation:

String.prototype.endsWith = function (s) {
  return this.length >= s.length && this.substr(this.length - s.length) == s;
}

using lastIndexOf just creates unnecessary CPU loops if there is no match.

ANSWER:

  1. Unfortunately not.
  2. if( "mystring#".substr(-1) === "#" ) {}