JS: String.prototype.includes

New in JS2015.

str.includes(searchString)

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

console.log("abcd".includes("cd") === true);
console.log("abcd".includes("x") === false);

str.includes(searchString , position)

Start search at position.

console.log("abcd".includes("cd", 3) === false);