如何使 array.forEach(async fn) 同步？

假设我有一个数组，我想对数组的每个元素执行异步函数。

let a = [x1, x2, x3]

// I want to
await a.forEach(async (x) => {...})

// which equals to
let fn = async (x) => {...}
await fn(x1)
await fn(x2)
await fn(x3)

我怎样才能做到这一点？

像这样？

for (let x of a) {
  await fn(x);
}

或者，如果您真的不喜欢创建一个单独的fn:

for (let x of a) {
  await (async v => {
    ...
  })(x);
}

你甚至可以将它添加到Array.prototype:

Array.prototype.resolveSeries = async function(fn) {
  for (let x of this) {
    await fn(x);
  }
}

// Usage:
await a.resolveSeries(fn);

// Or:
await a.resolveSeries(async x => {
  ...
});