Question

I know this works, but I don’t know why or the reasoning behind why it was made to work this way:

var foo = [5, 10];
var bar = foo;
console.log(foo); //[5, 10]
console.log(bar); //[5, 10]
bar[0] = 1; 
console.log(foo); //[1, 10]
bar = null;
console.log(foo); //[1, 10]

I would have expected not just bar to become null, but foo as well. I’d love some help understanding this.

Answer 1

The difference is between rebinding and mutating operations.

bar[0] = 1

is mutating; it affects the object that bar points to.

bar = null

is rebinding; it just affects what the identifier bar means.