node.js - 我使用异步 waterfall ，为什么回调不是函数？

Question

我明白了:

Error: TypeError: callback is not a function

代码:

var async = require('async');

async.waterfall([
  (callback) => {
    callback(null, 'test');
  },
  async (value1, callback) => {
    const data = await send("http://google.com/search?q="+value1);

    callback(null, data); //TypeError: cb is not a function
  }
], (err) => {
  if (err) throw new Error(err);
});

为什么会出现错误？尽管“回调”是 async.waterfall 的默认功能。难道在异步函数中我把异步函数放进去是不可能的吗？

Answer 1

当您在 waterfall 内的函数中使用async时，没有callback参数。您无需调用 callback(null, data)，而是解析 data。

async.waterfall([
  (callback) => {
    callback(null, 'test');
  },
  async value1 => {
    const data = await send("http://google.com");

    return data;
  },
  (value1, callback) => {
     // value1 is the resolve data from the async function
  }
], (err) => {
  if (err) throw new Error(err);
});

来自docs :

Wherever we accept a Node-style async function, we also directly accept an ES2017 async function. In this case, the async function will not be passed a final callback argument, and any thrown error will be used as the err argument of the implicit callback, and the return value will be used as the result value. (i.e. a rejected of the returned Promise becomes the err callback argument, and a resolved value becomes the result.)