Question

Hi i have a javascript code like this

    var a=10;
    var b="100";        
    document.write(b-a);

Actually it should show an error when we are subtracting a number from a string but it is showing as 90 as output but when we do b+a it is showing 10010 as output what is this behaviour.

Answer 1

When you subtract, Javascript attempts to cast the String b to Number, because there is no - operation defined for String.

When you use the + sign, Javascript attempts to cast the Number a to a String, because + is defined as concatenation for a String.