[javascript] 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?

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.

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

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');

And

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

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

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 jsperf.com

I made a jsben.ch for you http://jsben.ch/#/aWxtF ...seems that indexOf is a bit faster.

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

var re = /(AND|OR|MAYBE)/;
var str = "IT'S MAYBE BETTER WAY TO USE .MATCH() METHOD TO STRING";
console.log('Do we found something?', Boolean(str.match(re)));

Wish you a nice day, sir!

The Fastest

1. (ES6) includes

    var string = "hello",
    substring = "lo";
    string.includes(substring);

2. ES5 and older indexOf

    var string = "hello",
    substring = "lo";
    string.indexOf(substring) !== -1;

http://jsben.ch/9cwLJ