Positive Number to Negative Number in JavaScript?

Question

Basically, the reverse of abs. If I have:

if ($this.find(\'.pdxslide-activeSlide\').index() < slideNum - 1) {
  slideNum = -slideNum
}
console.log(slideNu         


        

Answer 1

Javascript has a dedicated operator for this: unary negation.

TL;DR: It's the minus sign!

To negate a number, simply prefix it with - in the most intuitive possible way. No need to write a function, use Math.abs() multiply by -1 or use the bitwise operator.

Unary negation works on number literals:

let a = 10;  // a is `10`
let b = -10; // b is `-10`

It works with variables too:

let x = 50;
x = -x;      // x is now `-50`

let y = -6;
y = -y;      // y is now `6`

You can even use it multiple times if you use the grouping operator (a.k.a. parentheses:

l = 10;       // l is `10`
m = -10;      // m is `-10`
n = -(10);    // n is `-10`
o = -(-(10)); // o is `10`
p = -(-10);   // p is `10` (double negative makes a positive)

All of the above works with a variable as well.