JS: String.prototype.includes

New in ES2015.

s.includes ( searchString )

s.includes ( searchString , position )

Returns true if s contains searchString, starting search at position. If omitted, it's 0. Else, returns false.

const g = "abcd";

console.log ( g.includes("cd") ); // true
console.log ( g.includes("cd", 3) ); // false

console.log ( g.includes("x") ); // false

Reference

ECMAScript 2015 §Text Processing#sec-string.prototype.includes