Javascript object property reset not working

Question

I have a javascript object called myObject. Inside that object i have a property called x that has a value of 0. After i have incremented x value by 1 i want to reset it back to 0, without accessing x to change it, but it does not work for some reason. I am using the Module Pattern.

var MyObject = (function(){

return {
     x:0
}
})();

var myObject = MyObject;

myObject.x+=1;
console.log(myObject.x); // shows value of 1

myObject = MyObject;  // object property reset
console.log(myObject.x); // shows value of 1, but i want 0

user6586783 · Accepted Answer · 2016-11-20 20:39:13Z

3

You are not resetting your object. You need to call the function each time.

var MyObject = (function() {
  return {
    x: 0
  }
});

var myObject = MyObject();
myObject.x += 1;
console.log(myObject.x); // shows value of 1

myObject = MyObject(); // object property reset
console.log(myObject.x); // shows value of 0

answered Nov 20, 2016 at 20:39

user6586783

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7 Comments

rabbitco Over a year ago

This answer is wrong. OP is using an IIFE to assign a value to MyObject and therefore the value of MyObject is not a function and consequently trying to do myObject = MyObject(); will result in TypeError: MyObject is not a function

JJWesterkamp Over a year ago

@rabbitco In this example, although the function is inside parentheses (expression), it is not being invoked, so MyObject gets assigned the value that expression evaluates to, which is indeed a function.

rabbitco Over a year ago

@JeffreyWesterkamp: That is incorrect. OP code is var MyObject = (function() {return {x: 0}})();. So it is invoked. Copy paste OP's code and run it and you will see for yourself.

JJWesterkamp Over a year ago

Yes it is, but in this answer it is not. That's what I meant, this answer actually should work.

rabbitco Over a year ago

@JeffreyWesterkamp: ok you are right about that. But the answer leaves the impression that OP - in his own code - just needs to change myObject = MyObject; to myObject = MyObject(); and that won't work.

|

Community · Accepted Answer · 2017-05-23 12:30:21Z

Javascript object reset not working

That is because you are re-assigning a reference to the same object.

What your are overlooking in your code

You are using an IIFE (Immediately-Invoked Function Expression) to initially assign the value {x: 0} to MyObject. You are not assigning a function to MyObject:

var MyObject = (function() {
  return {
    x: 0
  }
})();

console.log(MyObject); // { x: 0 }

That is because the IIFE only executes once and then ceases to exist. When you then do var myObject = MyObject; you are not creating a copy of MyObject but just another reference to the object { x: 0 }:

var a = {x: 0};
var b = a;

console.log(b); // {x: 0}

b.x = 10;

console.log (a); // 10
console.log (b); // 10

That is why your myObject = MyObject; does not reset anything because you are actually just restating that myObject should point to the same object as MyObject.

How you can make it work

Change your code to:

var MyObject = function(){
    return {x: 0}
}

var myObject = MyObject();

myObject.x+=1;
console.log(myObject.x); // 1

myObject = MyObject();  
console.log(myObject.x); // 0

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