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 +(plus sign) is also the string concatenation operator, while the -(minus sign) only applies to subtraction. If JavaScript can append 2 strings together it won't complain, but if you try to subtract 2 strings, it just doesn't make any sense.