Javascript String Assignment Operators

Question

How come I can use += on a string, but I cannot use -= on it?

For example...

var test = \"Test\";
var arr = \"⇔\"         


        

Answer 1

Because the + operator concatenates strings, but the - operator only subtracts numbers from each other.

As to the why -- probably because it is difficult to determine what people want to do when they subtract strings from each other.

For example:

"My string is a very string-y string" - "string"

What should this do?