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

Question

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?

Answer 1

You have three possibilites:

1. Regular expression:

    (new RegExp('word')).test(str)
    // or
    /word/.test(str)
   

2. indexOf:

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

3. includes:

    str.includes('word')
   

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

Performance test - short haystack
Performance test - long haystack

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**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.

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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)