为何Node.js的回调函数第一个参数是err

Question

fs.readFile('/etc/passwd', function (err, data) {
  if (err) throw err;
  console.log(data);
});

在node.js中为何回调函数的第一个参数是err（错误）？

Answer 1

It’s all because ES6 came late

Answer 2

This is a convention~~~
When using callbacks,
first check whether the error exists, and if it exists, process the error message;
Otherwise, follow the normal business logic

Answer 3

Personally, if the api is designed

fs.readFile('/etc/passwd').success(function(data){
    //todo
}).error(function(err){
    //todo
});

It will be more elegant.

Answer 4

Required parameters are listed in the front, and optional parameters are listed in the back. All APIs passed are designed according to this principle