传播和休息运算符

const nums = [5,6,7];const newnums = [1,2, nums[0],nums[1],nums[2]];console.log(newnums); // [ 1, 2, 5, 6, 7 ]is reduced to const nums = [5,6,7];const newnums = [1,2, ...nums];console.log(newnums); // [ 1, 2, 5, 6, 7 ]console.log(...newnums); // 1 2 5 6 7

const arr1 = [1,2,3,4,5];const arr2 = [6,7,8,9];let nums = [...arr1,...arr2];nums; // [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ]const firstname = "peter";const fullname = [...firstname,' ',"p."];fullname; // [ 'p', 'e', 't', 'e', 'r', ' ', 'p.' ]console.log(...firstname); // 'p' 'e' 't' 'e' 'r'

const girl = {  name: 'melania',  friends: ['alina', 'alice', 'ayesha', 'anamika', 'anaya']};const frnz = [...girl.friends];console.log(frnz); // [ 'alina', 'alice', 'ayesha', 'anamika', 'anaya' ]console.log(girl.friends); // [ 'alina', 'alice', 'ayesha', 'anamika', 'anaya' ]

let male = {  "firstname": "gangadhar",  "lastname": "shaktimaan"}let female = {  "firstname": "geeta",  "lastname": "vishwas"}let x = {...male, born: 1950};let y = {...female, born: 1940};x; // { firstname: 'gangadhar',   lastname: 'shaktimaan',   born: 1950 }y; // { firstname: 'geeta',  lastname: 'vishwas',  born: 1940 }```## shallow copy of objects:let male = {  "firstname": "gangadhar",  "lastname": "shaktimaan"}let character = {...male, firstname: 'wonderwoman'};male;         // { firstname: 'gangadhar', lastname: 'shaktimaan' }character;    // { firstname: 'wonderwoman', lastname: 'shaktimaan' }- first name for character object is changed although it was extracted from male object

## rest syntax collects all the elements after the last elements into an array. doesn't include any skipped elements. - hence, it should be the last element in the destructuring assignment.- there can be only one rest in any destructuring assignment.

- rest also works with objects. only difference is that elements will be collected into a new object instead of an arrray.

- although both look same, but they work differently based on where they are used.