JavaScript: String.prototype.includes

New in JS2015.

str.includes(searchString)

Return true if str contains searchString. Else, return false.

str.includes(searchString , position)

Start search at position.

const ss = "abcd";

console.log(ss.includes("cd") === true);
console.log(ss.includes("cd", 3) === false);
console.log(ss.includes("x") === false);