解构赋值
let input = [1, 2]; let [first, second] = input; console.log(first); // outputs 1 console.log(second); // outputs 2
上面的写法等价于:
first = input[0]; second = input[1];
利用解构赋值交换变量:
[first, second] = [second, first];
函数参数解构:
function f ([first, second]: [number, number]) [ console.log(first) console.log(second) ] f(1, 2)
解构剩余参数:
let [first, ...rest] = [1, 2, 3, 4] console.log(first) // 1 console.log(rest) // [2, 3, 4]
也可以忽略其它参数:
let [first] = [1, 2, 3, 4]; console.log(first); // outputs 1
或者跳过解构:
let [, second, , fourth] = [1, 2, 3, 4]
let o = { a: "foo", b: 12, c: "bar" }; let { a, b } = o;
就像数组解构,你可以用没有声明的赋值:
let a: number, b: number; ({a, b} = {a: 123, b: 456}) console.log(a, b) // 123 456
let { a, ...passthrough } = o;
let total = passthrough.b + passthrough.c.length;
属性解构重命名
你也可以给属性以不同的名字:
let { a: newName1, b: newName2 } = o;
let {a, b}: {a: string, b: number} = o;
function keepWholeObject(wholeObject: { a: string, b?: number }) { let { a, b = 1001 } = wholeObject; }
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展开数组
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展开对象
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不会展开方法
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解构赋值用于函数声明
type C = {a: string, b?: number} function f ({a, b}: C): void { // ... }