js 中连续的 3 个点 three dots (...) in javascript

Posted 2022-12-05 hangj

https://dev.to/sagar/three-dots---in-javascript-26ci

5 种用法

1

function myFunc(...[x, y, z]) 
  return x * y* z;


myFunc(1)          // NaN
myFunc(1, 2, 3)    // 6
myFunc(1, 2, 3, 4) // 6 (fourth parameter is not destructured)

2

function myFunc(x, y, ...params)  // used rest operator here
  console.log(x);
  console.log(y);
  console.log(params);


var inputs = ["a", "b", "c", "d", "e", "f"];
myFunc(...inputs); // used spread operator here
// "a"
// "b"
// ["c", "d", "e", "f"]

3

const featured = ['Deep Dish', 'Pepperoni', 'Hawaiian'];
const specialty = ['Meatzza', 'Spicy Mama', 'Margherita'];

const pizzas = [...featured, 'veg pizza', ...specialty];

console.log(pizzas); // 'Deep Dish', 'Pepperoni', 'Hawaiian', 'veg pizza', 'Meatzza', 'Spicy Mama', 'Margherita'

4

var obj1 =  foo: 'bar', x: 42 ;
var obj2 =  foo: 'baz', y: 13 ;

var clonedObj =  ...obj1 ;
// Object  foo: "bar", x: 42 

var mergedObj =  ...obj1, ...obj2 ;
// Object  foo: "baz", x: 42, y: 13 

5

[a, b, ...rest] = [10, 20, 30, 40, 50];
console.log(rest); // [30,40,50]

let a, b, ...rest = a: 10, b: 20, c: 30, d: 40
console.log(a); // 10 
console.log(b); // 20 
console.log(rest); //  c: 30, d: 40