动态对象名称属性不起作用

Question

I have a function through which I pass some variables as arguments. I need some of those to become variable names or object property names.

key(500, 'door', 10, 'bounceOut', 'regY', -150, 5, 'bounceIn');
function key(point, instance, speed, ease, prop, value, speed2, ease2, prop2, value2){
        ani.instance = true;
        createjs.Tween.get(instance, {override: true}).to({prop: value}, -(value + -instance.prop) * speed, createjs.Ease.ease);
    }

The solution stated here should have worked, but it does nothing for me.

 // ani.instance changed to:
    ani[instance]; // no error here
    // instance.prop changed to:
    instance[prop]; // returns 'undefined', expected it to return 'door[regY]'. instance and prop return 'door' and 'regY' respectively though

What is going on here? Can anyone nudge me in the right direction? Thank you :)

EDIT What I want the code to read is:

door.regY = 200;
createjs.Tween.get(door, {override: true}).to({regY: -150}, -(-150 + -door.regY) * 10, createjs.Ease.bounceOut);

Answer 1

In ES5 , You can only create or fetch "dynamic properties" on an object . So you need an object , or use this. with the [] notation.

var prop = "something";

this[prop] ="my value";

//this.something=== "my value"

var obj = {};

obj[prop] = "a value";

// obj.something === "a value";

var obj1 = {prop:"value"} 
// will not make obj.something === "value" 
// but obj.prop==="value" because in this case prop cannot be a variable

so you need to do something like that :

var arg1 = {};
arg1[prop]=value2;
var arg2 = {}
arg2[prop] = value2;
createjs.Tween.get(instance, arg1).to(arg2, -(value2 + -door[prop]) * 10, createjs.Ease.ease);

and so on , you need to define the objects before passing them to createjs.Tween.get method.

instance probably needs to be an object and not a string but since i know neither createJS or your script i cant tell.

EDIT : read this : http://www.jibbering.com/faq/faq_notes/square_brackets.html

Answer 2

In the invokation of your key function, you're passing a string as the instance argument. Thus, you will be able to access properties of the string, not your door object.

I assume there's a door object since you probably have such an object somewhere else, which has the property you're trying to access inside key ( regY in your example). You should be calling key like this, then:

key(500, door, 10, 'bounceOut', 'regY', -150, 5, 'bounceIn');

where door is a variable referencing that other object. Of course, you wouldn't know the variable name inside key then. If you also need that, you'll need to pass it as a different parameter. However, it doesn't sound like a good decision, do you actually need it?