javascript中的回调函数从何处获取其参数？

Question

I am able to run a code like this

myObject.save(function(error, data){
    if(error){
      console.log(error);
    }
    else {
      console.log(data);
    }
});

What i don't understand is where the anonymous function get the arguments error and data from?

Answer 1

Its from the thing that calls it - so save might look like this:

    function save(callback) {
        //do stuff

        var error = false;
        var data = {
            something: 'horse'
        };

        callback(error, data)
    }

There's no magic going on - its just a function call