spread_operator.js

var cityNames = ['Mumbai', 'Delhi', 'Pune', 'Ahmadabad', 'Indore'];
console.log(...cityNames); // Mumbai Delhi Pune Ahmadabad Indore 

var numbers = [22, 11, 98, 43, 87, 56, 45, 01, 24];
// Without spread operator
console.log("Smallest no.:",Math.min(numbers)); // Smallest no.: NaN
// With spread operator 
console.log("Smallest no.:",Math.min(...numbers)); // Smallest no.: 1

// copy an array
var arr = [10, 20 ,30 ];
var newArr = [...arr];
console.log(newArr); //[ 10, 20, 30 ]

// concat an array
var city1 = ['Mumbai', 'Pune', 'Delhi'];
var city2 = ['Surat', 'Ahmadabad', 'Kutchh'];

newCity = [...city1, ...city2, 'Thane']; //same as city1 = city1.concat(city2)
console.log(newCity); //[ 'Mumbai', 'Pune', 'Delhi', 'Surat', 'Ahmadabad', 'Kutchh', 'Thane' ]

//clone object
let cityObj = { city: 'Mumbai', state: 'MH' };
let clonedObj = { ...cityObj };
console.log(clonedObj); //{ city: 'Mumbai', state: 'MH' }

let cityObj1 = { city: 'Mumbai', state: 'MH' };
let cityObj2 = { town: 'Unr', state: 'MH' };

let newClonedObj = { ...cityObj1, ...cityObj2 };
console.log(newClonedObj); //{ city: 'Mumbai', state: 'MH', town: 'Unr' }