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: 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;
};
}
/#$/.test(str)
will work on all browsers, doesn't require monkey patching String
, and doesn't require scanning the entire string as lastIndexOf
does when there is no match.
If you want to match a constant string that might contain regular expression special characters, such as '$'
, 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)
- Unfortunately not.
if( "mystring#".substr(-1) === "#" ) {}