what is the easiest way to figure out if a string ends with a certain value?
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8 Answers
you could use Regexps, like this:
str.match(/value$/)
which would return true if the string has 'value' at the end of it ($).
4 Comments
gmunkhbaatarmn
Fail test: value="test[a-z]". Otherwise: 'test[a-z]'.match(/[a-z]$/) is return "null"
diclophis
I don't normally grab the regex tool out of my bag first, but this beats all the alternatives (String#endsWith is supported natively only in firefox, and extending / using 3rd party js is a bit overkill)
Jonathan.Brink
match() does not return a boolean. 'foobar'.match(/bar$/) returns ["bar"]
mitaka
RegEx Search() instead of Match() would be a better option if we just want a boolean result. Search() will return -1 if there is no found. if(str.search(/value$/) != -1) developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
Stolen from prototypejs:
String.prototype.endsWith = function(pattern) {
var d = this.length - pattern.length;
return d >= 0 && this.lastIndexOf(pattern) === d;
};
'slaughter'.endsWith('laughter');
// -> true
4 Comments
Walter Rumsby
Some people believe that modifying the prototype of a core class is something that you shouldn't do - Crockford refers to this as "global abatement" in his book JavaScript: The Good Parts.
Luca Matteis
Why shouldn't you do it? Or you just don't do it because Crockford said it?
NickFitz
You shouldn't do it as it isn't guaranteed to work in all implementations of JS: the ECMAScript Compact Profile spec (ECMA-327: ecma-international.org/publications/standards/Ecma-327.htm) specifies that "Compact" implementations (e.g. on handheld devices such as phones) need not support it (see section 5.2). Even if you aren't bothered by that, it's quite possible that it will break newer versions of JS: for example, anybody who has in the past deployed code that adds a "forEach" method to Array.prototype is now breaking the native implementation in recent versions of Firefox.
studgeek
If someone doesn't want to modify String they can turn it into a standalone function very easily.
Regular expressions
"Hello world".match(/world$/)
Comments
I had no luck with the match approach, but this worked:
If you have the string, "This is my string." and wanted to see if it ends with a period, do this:
var myString = "This is my string.";
var stringCheck = ".";
var foundIt = (myString.lastIndexOf(stringCheck) === myString.length - stringCheck.length) > 0;
alert(foundIt);
You can change the variable stringCheck to be any string to check for. Better still would be to throw this in your own function like this:
function DoesStringEndWith(myString, stringCheck)
{
var foundIt = (myString.lastIndexOf(stringCheck) === myString.length - stringCheck.length) > 0;
return foundIt;
}
1 Comment
Nathan
Really nice, @theJerm. This worked for me in a variety of situations whereas .match didn't always.
You can do 'hello world'.slice(-5)==='world'. Works in all browsers. Much faster than regex.
Comments
ES6 supports this directly:
'this is dog'.endsWith('dog') //true
2 Comments
ToniWidmo
This will be useful once no-one is using IE11 or below any more.
Mr. Goferito
Yup, but for that you have babel.
I am just expanding on what @luca-matteis has posted but to solve the issues pointed out in the comments the code should be wrapped to make sure you are not overwriting a native implementation.
if ( !String.prototype.endsWith ) {
String.prototype.endsWith = function(pattern) {
var d = this.length - pattern.length;
return d >= 0 && this.lastIndexOf(pattern) === d;
};
}
This is the suggested method for the Array.prototype.forEach method pointed out in the mozilla developer network
Comments
You can always prototype String class, this will work:
String.prototype.endsWith = function(str) {return (this.match(str+"$")==str)}
You can find other related extensions for String class in http://www.tek-tips.com/faqs.cfm?fid=6620
