Question

Are javascript objects value based or reference based? For example:

obj1.list =new array();
// ------ populate list
obj2.list = obj1.list

Does the browser make different copy of the obj1.list for obj2.list, or is obj2.list just a reference to obj1.list?

Answer 1

JavaScript Objects (and by extension: arrays, regexes, dates, non-primitive strings/numbers/booleans etc.) equality and assignment are reference based:

{a:'a'} == {a:'a'} // false

But:

var myObject = {a:'a'};
var myObject2 = myObject;

myObject == myObject2 // true

Furthermore:

myObject.b = 'b';

console.log(myObject2.b); // Logs: "b"