Question

我有一个值数组，我想创建一个promises数组来进行并行调用。但为什么地图功能不起作用？

let myArray = [1,2,3];
myArray.map((n) => {
    return new Promise((resolve, reject) => {
        resolve(n);
    });
});
console.log(myArray); // [1,2,3]

但是当我尝试将Promise推送到数组时可以按预期工作。

let myArray = [1,2,3];
let pArray = []
for(let n of myArray){
    pArray.push(new Promise((resolve, reject) => {
        resolve(i);
    }));
}
console.log(pArray); // [Promise,Promise,Promise]

Answer 1

这样做，因为map不修改数组：

let myArray = [1,2,3];
let promiseArray = myArray.map((n) => {
    return new Promise((resolve, reject) => {
        resolve(n);
    });
});
console.log(promiseArray);

Answer 2

您需要指定map的结果。

let myArray = [1, 2, 3];
let pArray = myArray.map((n) => {
  return new Promise((resolve, reject) => {
    resolve(n);
  });
});
console.log(pArray); // [Promise,Promise,Promise]

Array.prototype.map不能用于Promise？

2 个答案: