执行上下文在简单示例中如何显示

Question

thank you for helping me out.

In a class I am taking I have come across the following code:

var carlike = function(obj, loc){
    obj.loc = loc;
    obj.move = move;
    return obj;
};

var move = function(){
    this.loc++;
};

var ben = carlike({}, 9);

It is my understanding that when the function carlike is invoked on the last line during the creation phase of its execution context the variable move is set to undefined . So my question is: at which point is move set equal to function() {this.loc++;}; ? I find this confusing since the move function is defined after the carlike function. So how does carlike have access to the environment after it.

I really would like to know how this works under the hood in terms of the execution context, scope etc.

some things I have read to try and understand this:

http://dmitrysoshnikov.com/ecmascript/chapter-1-execution-contexts/ http://corporate.tuenti.com/en/dev/blog/functions-and-execution-contexts-in-javascript-2

Answer 1

It has access to that move variable because although the function move is declared after the function carlike, the function carlike does not reference move until after move has already been declared, since carlike is called after move is defined as a function. If you make the call to carlike above the definition of move, then move will be set to undefined, since that function does not exist yet.