Fastest way to check a string contain another substring in JavaScript?

I'm working with a performance issue on JavaScript. So I just want to ask: what is the fastest way to check whether a string contains another substring (I just need the boolean value)? Could you please suggest your idea and sample snippet code?



You have two possibilites:

  1. Regular expression:

    (new RegExp('word')).test(str)
    // or
  2. indexOf:

    str.indexOf('word') !== -1

Regular expressions seem to be faster (at least in Chrome 10).

Performance test - short haystack
Performance test - long haystack

Update 2011:

It cannot be said with certainty which method is faster. The differences between the browsers is enormous. While in Chrome 10 indexOf seems to be faster, in Safari 5, indexOf is clearly slower than any other method.

You have to see and try for your self. It depends on your needs. For example a case-insensitive search is way faster with regular expressions.

Update 2018:

Just to save people from running the tests themselves, here are the current results for most common browsers, the percentages indicate performance increase over the next fastest result (which varies between browsers):

Chrome: indexOf (~98% faster) <-- wow
Firefox: cached RegExp (~18% faster)
IE11: cached RegExp(~10% faster)
Edge: indexOf (~18% faster)
Safari: cached RegExp(~0.4% faster)

Note that cached RegExp is: var r = new RegExp('simple'); var c = r.test(str); as opposed to: /simple/.test(str)


Does this work for you?

string1.indexOf(string2) >= 0

Edit: This may not be faster than a RegExp if the string2 contains repeated patterns. On some browsers, indexOf may be much slower than RegExp. See comments.

Edit 2: RegExp may be faster than indexOf when the strings are very long and/or contain repeated patterns. See comments and @Felix's answer.


The Fastest

  1. (ES6) includes
    var string = "hello",
    substring = "lo";
  1. ES5 and older indexOf
    var string = "hello",
    substring = "lo";
    string.indexOf(substring) !== -1;

enter image description here


In ES6, the includes() method is used to determine whether one string may be found within another string, returning true or false as appropriate.

var str = 'To be, or not to be, that is the question.';

console.log(str.includes('To be'));       // true
console.log(str.includes('question'));    // true
console.log(str.includes('nonexistent')); // false

Here is jsperf between

var ret = str.includes('one');


var ret = (str.indexOf('one') !== -1);

As the result shown in jsperf, it seems both of them perform well.


For finding a simple string, using the indexOf() method and using regex is pretty much the same: - so choose which ever one that seems easier to write.


I made a for you ...seems that indexOf is a bit faster.


It's easy way to use .match() method to string.

var re = /(AND|OR|MAYBE)/;
console.log('Do we found something?', Boolean(str.match(re)));

Wish you a nice day, sir!


I've found that using a simple for loop, iterating over all elements in the string and comparing using charAt performs faster than indexOf or Regex. The code and proof is available at JSPerf.

ETA: indexOf and charAt both perform similarly terrible on Chrome Mobile according to Browser Scope data listed on


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