javascript what happens on array push?

so I have:

var something = function () { return 6}

var foo = new something();

var arr = []
var arr2 = []

I do arr2.push(foo) and arr.push(foo)

What happens in the background? Is foo dupl开发者_开发技巧icated and put in 2 places? Is foo just foo and what's inside the arrays a reference to foo?

Thanks.

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EDIT: I misread. Because you are invoking the function with new you create a new object. Any object is passed by reference.

var something = function () { return 6}

var foo = new something();

typeof foo is an object so in this case it is passed by reference.

Pretty sure that foo is duplicated since it's a primitive and not an object.

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What's inside the arrays are references to the same instance of something. This can be checked easily using for example chrome javascript console...

As you can see adding a new member x to arr1[0] got it appearing on arr2[0].