解构数组

  • 解构数组元素
let input = [1, 2];
let [first, second] = input;
console.log(first,second);
  • 交换值
[first, second] = [second, first];
  • 函数参数解构
function f([first, second]: [number, number]){
console.log(first,second);
} f([1,2]);
  • 剩余变量
let [first, ...rest] = [1,2,3,4];
console.log(first,rest);
  • 忽略尾随元素
let [first] = [1,2,3,4];
console.log(first);
  • 忽略其他元素
let [, second, , fourth] = [1,2,3,4];
console.log(second,fourth);

解构元组

  • 解构元组元素
let tuple: [number, string, boolean] = [7, "hello", true];
let [a, b, c] = tuple;
  • 剩余元素
let [a, ...bc] = tuple;
let [a,b,c, ...d] = tuple;
  • 忽略末尾元素或其他元素
let [a] = tuple;
let [, b] = tuple;

对象解构

  • 解构对象属性
let o = {
a: "foo",
b: 12,
c: "bar"
} let {a, b} = o;
  • 解构赋值
({a, b} = {a:"baz",b:101});
  • 剩余变量
let {a, ...passthrough} = o;
let total = passthrough.b + passthrough.c.length;
  • 解构属性重命名
let {a:newName1, b:newName2} = o;
  • 解构并指定类型
let {a, b}: {a:string, b:number} = o;
  • 解构并赋予默认值
function keepWholeObject(wholeObject: {a:string, b?:number}){
let {a,b = 1001} = wholeObject;
}

函数声明解构

  • 函数声明解构
type C = {a:string, b?: number}
function f({a,b}: C): void{
}
  • 指定默认值
function f({ a="", b = 0} = {} ): void{
} f(); function f({a,b = 0 } = {a: "" }): void {
}

展开数组

  • 数组元素展开
let first = [1, 2];
let second = [3, 4];
let bothPlus = [0, ...first, ...second, 5];
  • 对象展开
let defaults = {food: "spicy" ,price : "$$" , ambiance: "noisy" };
let search = {...defaults, food: "rich" };
  • 对象展开(但布包含方法)
class C {
p = 12;
m() {
}
} let c = new C();
let clone = {...c};
clone.p;
clone.m(); // error!
05-13 03:15