New Function in ES6

repeat()

console.log("x".repeat(3));         // "xxx"
console.log("hello".repeat(2));     // "hellohello"

Object.is()

When you want to compare two values, you’re probably used to using either the equals operator (==) or the identically equals operator (===). Many prefer to use the latter to avoid type coercion during the comparison. However, even the identically equals operator isn’t entirely accurate. For example, the values +0 and -0 are considered equal by === even though they are represented differently in the JavaScript engine. Also NaN === NaN returns false, which necessitates using isNaN() to detect NaN properly.

In many cases, Object.is() works the same as ===. The only differences are that +0 and -0 are considered not equivalent and NaN is considered equivalent to NaN. Here are some examples:

console.log(+0 == -0);              // true
console.log(+0 === -0);             // true
console.log(Object.is(+0, -0));     // false

console.log(NaN == NaN);            // false
console.log(NaN === NaN);           // false
console.log(Object.is(NaN, NaN));   // true

console.log(5 == 5);                // true
console.log(5 == "5");              // true
console.log(5 === 5);               // true
console.log(5 === "5");             // false
console.log(Object.is(5, 5));       // true
console.log(Object.is(5, "5"));     // false