New Objects Get Overwritten When Being Added To An Array

Newbie here...be nice. I have an empty object that will get pushed into an array. listView = {}; I add properties to it. listView.code = code; listView.description = description;

Solution 1:

You are always adding a reference to the same object, and changing that same object, instead of adding new objects. See this:

var a = [];
var o = {};
for (var i = 0; i < 5; i++) {
  o.id = i;
  a.push(o);
}
a
// => [{"id":4},{"id":4},{"id":4},{"id":4},{"id":4}]

But

var a = [];
for (var i = 0; i < 5; i++) {
  var o = {};
  o.id = i;
  a.push(o);
}
a
// => [{"id":0},{"id":1},{"id":2},{"id":3},{"id":4}]

The difference is, the second code always makes a new object that is distinct from all other objects already in the array.

As a metaphor, imagine a theatre director in casting. He turns to an actor, says "You... you'll be Romeo.". Then he looks at the same actor, says "You... you'll be Mercutio. Here, Mercutio, take this sword. Romeo... who told you to get a sword?!?" completely failing to realise that, if Romeo and Mercutio are the same person, if one of them picks up a sword, the other does it too.

Solution 2:

Seeing as you declared yourself a 'newbie' i figured i'd take a bit more time explaining. When you push an object to an array, you don't copy the object. You just tell the array where to find the object (a reference). If you push the same object 3 times, the array just has 3 indexes at which it finds the same object. There's several ways around this, the easiest being that you declare the variable inside the loop

for (var i=0;i<3;i++){
    var listView = {};
    listView.id = i;
    listy.push(listView);
}

This way listView is a different reference each time. The other way is to create a new object when you push

listy.push({id:listView.id, description:listView.description});

which works because simple variables are 'copied' into the array and not referenced.

Solution 3:

your assignment of the properties of an object are simply replacing the existing properties. wh en you push the object in the array by name, you are push a reference to the object and not a value. This is why all the elements in the array are the same. You need to create a new object every time you push. Something like this should work for you.

listy.push({code:code, description:description});

Solution 4:

try this :

listy.push({
    code:listView.code,
    description : listView.description
})

In my code I have used pass by value.

In your code , you are using Objects which are passed by reference .

You are adding same reference again and again so at the end you will get an array having all the values of same object .

To understand more about pass by value and pass by reference you can reffer this link :

Pass Variables by Reference in Javascript