reactjs - 我的 reducer 中这个带有三个点的运算符是什么意思？

Question

我的 reducer 是这样的:

export const setName = action => {
  return {
    type: "SET_NAME",
    ...action
  };
};

这 3 个点和 reducer 在做什么？

Answer 1

Spread syntax allows an iterable such as an array expression or string to be expanded in places where zero or more arguments (for function calls) or elements (for array literals) are expected, or an object expression to be expanded in places where zero or more key-value pairs (for object literals) are expected.

函数示例:

function sum(x, y, z) {
  return x + y + z;
}

const numbers = [1, 2, 3];

console.log(sum(...numbers));
// expected output: 6

console.log(sum.apply(null, numbers));

对象示例

let a = {a: 1};
let b = {...a, b: 2};

console.log(b) //will print {a: 1, b: 2}

把它想象成将一个对象解压缩到另一个对象中。

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