JavaScript展开操作符(Spread operator)详解

const a = [1, 2, 3],
     b = [4,5,6];

const c = [...a] // [1,2,3]

const d = [...a，...b] // [1,2,3,4,5,6]

const d = [...a,4, 5, 6] // [1,2,3,4,5,6]

const a = [1,2,3];
a.push(...b);

const a = [1,2,3];
a. unshift(...b);

var list=document.getElementsByTagName('a');
var arr=[..list];

const newObj = { ...oldObj }

const obj1 = { a: 111, b: 222 };
const obj2 = { c: 333, d: 444 };
const merged = { ...obj1, ...obj2 };
console.log(merged); // -> { a: 111, b: 222, c: 333, d: 444 }

const others = {third: 3, fourth: 4, fifth: 5}
const items = { first:1, second:1, ...others }
items //{ first: 1, second: 2, third: 3, fourth: 4, fifth: 5 }

const obj1 = { a: 111, b: 222 };
const obj2 = { b: 333, d: 444 };
const merged = { ...obj1, ...obj2 };
console.log(merged); // -> { a: 111, b: 333, d: 444 }

const obj1 = {a:111,b:222}
const merged = {a:222,...obj1}; 
console.log(merged); // -> { a: 111, b: 333 }

const obj1 = {a:111,b:222}
const merged = {...obj1,a:222}; 
console.log(merged); // -> { a: 222, b: 333 }

const hey = 'hey'
const arrayized = [...hey] // ['h', 'e', 'y']

const hey = 'hey'
const arrayized = hey.split('') // ['h', 'e', 'y']

const f = (foo, bar) => {}
const a = [1, 2]
f(...a)

const numbers = [1, 2, 3, 4, 5]
const sum = (a, b, c, d, e) => a + b + c + d + e
const sum = sum(...numbers)

var s = new Set();
s.add(1);
s.add(2);
var arr = [...s]// [1,2]


function * gen() {
  yield 1;
  yield 2;
  yield 3;
}

var arr = [...gen()] // 1，2，3

var m = new Map();
m.set(1,1)
m.set(2,2)
var arr = [...m] // [[1,1],[2,2]]

var obj = {'key1': 'value1'};
var array = [...obj]; // TypeError: obj is not iterable