js-spread-operator.js

// ************************************************
// ************** Spread operator *****************
// ************************************************

// Merging arrays

const reptiles = ['snake', 'lizard', 'alligator'];
const mammals = ['puppy', 'kitten', 'bunny'];

// ES5 approach:
const animals = [];
reptiles.forEach(oneReptile => animals.push(oneReptile));
mammals.forEach(oneMammal => animals.push(oneMammal));
console.log(animals); // [ 'snake', 'lizard', 'alligator', 'puppy', 'kitten', 'bunny' ]

// comment  out the previous when demo the next:
// ES6 approach using spread operator:
const reptiles = ['snake', 'lizard', 'alligator'];
const mammals = ['puppy', 'kitten', 'bunny'];
const animals = [...mammals, ...reptiles];
console.log(animals); // [ 'puppy', 'kitten', 'bunny', 'snake', 'lizard', 'alligator' ]

// Copying arrays
// .slice()
const names = ['ana', 'milo', 'ivan'];
const names2 = names.slice();
console.log(names2); // => [ 'ana', 'milo', 'ivan' ]

// spread  operator
const names = ['ana', 'milo', 'ivan'];
const names3 = [...names];
console.log(names3); // => [ 'ana', 'milo', 'ivan' ]