Why data binding doesn't always work with primitives?

Question

One of the milestones in learning JS and Angular, is learning that two way data binding with primitives is tricky. If you want to make sure that databinding works, you should always pack it into an object - that is what I was told by some seniors in my company. My question is - why is that happening? What is exactly going on that makes databinding with primitives so compliated in JS?

I found out that Javascript passes objects by reverence, and primitives by value. So what exactly happens in for example AngularJS Controller, that enables us to bind primitive in ngModel?

EDIT

Any articles, pointers are more than welcome!

Answer 1

Here is good post or post . In short:

"Primitive values (eg numbers, strings) are immutable in JavaScript. So whenever a change is made to them it means we are actually throwing away the previous instance and using a different one."