Javascript - [Why?] Assigning a variable to an object

Question

Why is it that when I assign a variable to an object and make a change to that variable it also changed the objects? For example:

c = 26;
a = b = c;
a += 1;

a      // 27
b      // 26
c      // 26

but

z = {};
x = y = z;
x.ab = 5; 

x      // Object {ab: 5}
y      // Object {ab: 5}
z      // Object {ab: 5}

Why (in the example above) does y.ab and z.ab exist? I only modified x not y or z. Howcome in the first example (with the integers), when I changed the value of a, b and c weren't affected?

Not a JS expert, but the Java explanaition would be that you are dealing not with objects but with references to the object, so `x` `y` and `z` all point to the only object that has been actually created — SJuan76, Jul 05 '14 at 12:29
Short answer: because a,b and c refer to an immutable scalar value, and x, y and z refer to a mutable object. — Robby Cornelissen, Jul 05 '14 at 12:29

score 2 · Accepted Answer · answered Jul 05 '14 at 12:29

2

When you assign an object to a variable, it just makes a reference to the original object, it doesn't make a copy. So all the variables refer to the same object.

answered Jul 05 '14 at 12:29

Barmar

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Javascript - [Why?] Assigning a variable to an object

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