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?

ECMAScript 6 introduced String.prototype.includes:



const string = "foo";
const substring = "oo";

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



String.prototype.includes is case-sensitive and is not supported by Internet Explorer without a polyfill.

In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found:



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

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

Stack Overflow Q#1789945, score: 16083