ES8 – Array and Exponent

ES8 aka. ES2017

Array.prototype custom function (review)

let number = [1, 2, 3, 4]; 
let moreNumbers = new Array (1, 2, 3, 4); 

Array.protype.count = function() { 
    return this.length;
}

console.log(numbers.count());     // outputs 4
console.log(moreNumbers.count()); // outputs 4

 

Array.prototype.includes

Check if an array contains a specific value and returns a boolean.

let letters = ['a', 'b', 'c', NaN]; 
letters.includes('b');      // true
letters.includes('d');      // false

// includes is similar to indexOf from older version 
letters.indexOf('b') >= 0   // true

// when includes and indexOf is different: 
letters.includes(NaN)       // true
letters.indexOf(NaN) >= 0   // false

 

Exponential syntax: **

3 ** 4 = Math.pow(3, 4)