How to check whether a string contains a substring in JavaScript?

Usually I would expect a String.contains() method, but there doesn't seem to be one.

What is a reasonable way to check for this?

Answer

ECMAScript 6 introduced String.prototype.includes:

var string = "foo",
    substring = "oo";


console.log(string.includes(substring));

includes doesn’t have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found:

var string = "foo",
    substring = "oo";

console.log(string.indexOf(substring) !== -1);