Unary Plus and Minus

+ is the unary plus. When the unary plus is applied to a nonnumeric value, it performs the same conversion as the Number() casting function.

 
<!DOCTYPE html>
<html>
<head>
    <title>Operator Example</title>
    <script type="text/javascript">

        var s1 = "2"; 
        var s2 = "A"; 
        var s3 = "2.1"; 
        var s4 = "0xAA"; 
        var b  =  true; 
        var b2 = false; 
        var f  = 1.1; 
        var o  = { 
            valueOf: function() { 
               return 10; 
            } 
        }; 
        
        document.writeln(s1);
        document.writeln(s2);
        document.writeln(s3);
        document.writeln(s4);
        document.writeln(b);
        document.writeln(b2);
        document.writeln(f);
        document.writeln(o);
        
        s1 = +s1; 
        s2 = +s2; 
        s3 = +s3; 
        s4 = +s4; 
        b  = +b; 
        b2 = +b2; 
        f = +f; 
        o = +o;

        document.writeln(s1);
        document.writeln(s2);
        document.writeln(s3);
        document.writeln(s4);
        document.writeln(b);
        document.writeln(b2);
        document.writeln(f);
        document.writeln(o);
        
    </script>

</head>
<body>
  
</body>
</html>

Click to view the demo

The unary minus operator negates a numeric value.

 
<!DOCTYPE html>
<html>
<head>
    <title>Operator Example</title>
    <script type="text/javascript">

        var num = 2; 
        num = -num; //becomes -2 
        document.writeln(num);
        
    </script>

</head>
<body>
  
</body>
</html>

Click to view the demo

When used on nonnumeric values, unary minus applies the same rules as unary plus:

 
<!DOCTYPE html>
<html>
<head>
    <title>Operator Example</title>
    <script type="text/javascript">

        var s1 = "2"; 
        var s2 = "A"; 
        var s3 = "2.1"; 
        var s4 = "0xAA"; 
        var b  =  true; 
        var b2 = false; 
        var f  = 1.1; 
        var o  = { 
            valueOf: function() { 
               return 10; 
            } 
        }; 
        
        document.writeln(s1);
        document.writeln(s2);
        document.writeln(s3);
        document.writeln(s4);
        document.writeln(b);
        document.writeln(b2);
        document.writeln(f);
        document.writeln(o);
        
        s1 = -s1; 
        s2 = -s2; 
        s3 = -s3; 
        s4 = -s4; 
        b  = -b; 
        b2 = -b2; 
        f = -f; 
        o = -o;

        document.writeln(s1);
        document.writeln(s2);
        document.writeln(s3);
        document.writeln(s4);
        document.writeln(b);
        document.writeln(b2);
        document.writeln(f);
        document.writeln(o);
        
    </script>

</head>
<body>
  
</body>
</html>

Click to view the demo