Warm tip: This article is reproduced from serverfault.com, please click

node.js-TypeError [ERR_INVALID_CALLBACK]:回调必须是一个函数。

(node.js - TypeError [ERR_INVALID_CALLBACK]: Callback must be a function. Received undefined in nodejs)

发布于 2020-11-28 06:04:09

嗨,大家好,我是node js的新手,尝试将我的文件追加到node js时出现错误,不知道怎么回事,请尝试修复我的错误,并告诉我该怎么办?

console.log("Starting app.js");

const fs = require('fs');
const os = require('os');
const notes = require('../notes-node/notes.js');

var user = os.userInfo();

fs.appendFile('message.txt', `Hello ${user.username}! You are ${notes.age}`)

console.log(user);
Questioner
user13427179
Viewed
33
Harshana Serasinghe 2020-11-28 14:22:15

你的fs.appendFile函数应具有一个回调函数作为第三个参数。

句法:

fs.appendFile( path, data[, options], callback )

你的JS文件应如下更改:

console.log("Starting app.js");

const fs = require('fs');
const os = require('os');
const notes = require('../notes-node/notes.js');

var user = os.userInfo();

fs.appendFile("message.txt", `Hello ${user.username}! You are ${notes.age}`, (err) => { 
  if (err) { 
    console.log(err); 
  } 
}); 

console.log(user);

有关更多信息fs.appendFilehttps : //nodejs.org/api/fs.html#fs_fs_appendfile_path_data_options_callback