Creating A Game - Object Changes By Itself - Shared Memory ?

I am creating a game in JavaScript!

It is going to be a clone of the game ChuChu Rocket! that I used to play on the Dreamcast.

The game is set up so that the levels sit inside a nested array of objects, like your typical JSON string. So that within levels[] there are objects with level names, an array of moveable items, an array of arrows you can place, etc.

I have set it up so that when the level is loaded in to the DOM, it also duplicates a part of the object, the part responsible for the positioning of the moveable items on screen so that when they are animated, and if there is a fail scenario (cat eats mouse, cat gets to rocket before mouse) you should be able to reset and it remembers your coordinates.

From what I have learned in my years of studying and using JavaScript, the following should always hold true: a=1; b=a; b++; // b would become 2, a would stay as 1 (they are separate variables)

I seem to have found an exception to this rule.

When creating a level, I duplicate the part of my object called o.chuchu and I call it o.chuchuMoving

If I make a change to anything in o.chuchuMoving, it also changes o.chuchu.

o.chuchu and o.chuchuMoving are arrays within the object. Formatted like this: [0,0,1],[1,0,1],[2,0,1],[3,0,1] ... etc

If I tell my object the following: o.chuchuMoving[0][0]=1... then o.chuchu[0][0] also becomes 1.

Please check the code at [url] when you get a moment