这个对象会一直调用该函数吗？

Question

Here is the first way:

var Objek = {
    node : document.getElementById(known_id),
}

So, when i call Objek.node does this always call the document.getElementById ?

Is this second way better? :

var Objek = (function() {
    var getNode = document.getElementById(known_id);


    return {
        node : getNode
    }
})();

I think this second way is better and wouldn't re-call the document.getElementById when I call Objek.node

Answer 1

In both cases getElementById() is called only once (when you create the object, not when you use objek.node).

In first case ONLY getElementById() is called and value assigned into new object...

...while in second case first your function is called, then getNode variable is created, then getElementById() is called and result is assigned to variable and at last new object is created with given property.

So actually first case is both faster to execute and better to understand by developers.

Answer 2

They are equivalent. In both the getElementByIdmethod is called only one time (when you create the object) and then the stored value in the variable is returned at all times when you do Objek.node