What does immutable mean?

Question

If a string is immutable, does that mean that.... (let\'s assume JavaScript)

var str = \'foo\';

alert(str.substr(1)); // oo

alert(str); // foo

Answer 1

Immutable means that which cannot be changed or modified.

So when you assign a value to a string, this value is created from scratch as opposed to being replaced. So everytime a new value is assigned to the same string, a copy is created. So in reality, you are never changing the original value.