Operators

ES6 Spread Operator

ES6 Equivalent Spread Operator

const sum3 = addFourAges(...ages);
// the ... means the ages array is expanded into individual components.

Join two Arrays

const arrayOne= ['hello', 'two'];
const arrayTwo = ['three', 'four'];
const arrayThree = [...arrayOne, ...arrayTow];

Looping through all elements and changing the color

const h = document.querySelector(h1)
const boxes = documwnt.querySelectorAll('.box');

const all = [h, ...boxes];
Array.form(all).forEach(cur=> cur.style.color='purple') // returns an array

Rest Parameter

function isFullAge(...years){
years.forEach(cur=> (216-cur)>=18);
}
 isFullAge(1990,1921,1967);

Default Parameters =

function Person(first, last = 'lastname'){
this.firstname = first;
this.lastname = last;

}

Maps

New key value data structure

const question = new Map();
question.set('question', 'what is');
question.set(1,'es5);
question.set(2, 'es6');
question.set(3, 'ES2015');
question.set('correct', 3);
question.set(True, 'Correct Answer');
question.set(false, 'wrong');

// Retrieve DAta
question.get('question')
// get size
question.size;

// delete 
question.delete(2);

// delete All
question.clear();

// loop

question.forEach((value,key)=> console.log(`this ${key}, and its set ot ${vlaue})

// Another Way to Loop
for(let[key, value]of question.entries()){
console.log(`this ${key}, and its set ot ${vlaue});
if(typeof(key)=== 'number'){
console.log(`Answer ${key}, and its set ot ${vlaue});
}