NodeJS 中的回调

Question

I have an async function

function(word,callback)
{
  setTimeout(3000, function()
  {
      console.log("waiting");
  }
  callback(null, word);
}

function f2 (err, result){
  console.log(result);
}

What is the result?
How does callback know I am referring to f2 ?

Answer 1

There is no result. That code won't even compile.

Even if you fix the syntax errors, you never call any functions.

Assuming you fixed all of that, it would know that you were referring to f2 because you would be explicitly passing it as the second argument.

function my_function_that_accepts_a_callback (word, callback) {
    setTimeout(3000, function() {
            console.log("waiting");
        }
        callback(null, word);
    }
}

function f2(err, result) {
    console.log(result);
}

my_function_that_accepts_a_callback("this is a word", f2);