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ECMAScript 2016 (ES7)

Array.prototype.includes()

This feature introduces a more readable syntax for checking if an array contains an element.

With ES6 and lower, to check if an array contained an element you had to use indexOf, which checks the index in the array, and returns -1 if the element is not there.

With this feature introduced in ES7 we can do

if (![1, 2].includes(3)) {
  console.log("Not found");
}

Exponentiation Operator

The exponentiation operator ** is the equivalent of Math.pow(), but brought into the language instead of being a library function.

Math.pow(4, 2) == 4 ** 2;