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Convert negative number to positive in JavaScript

April 26, 2021  ‐ 1 min read

Sometimes you may need to turn a negative number into a positive one. Of course there is the high(or elementary?) school mathematics approach: multiplying two negative numbers gives a positive.

let x = -5;
x *= -1;
console.log(x); // => 5

But this only guarantees a positive number if you are sure that your variable is negative. Otherwise you will a negative and positive number which gives a negative obviously.

In that case you may use the Math.abs() function that comes with JavaScript to convert negative number to positive. The Math.abs() function returns the absolute value of the number you pass it as a parameter.

If you pass a negative number to Math.abs() it returns the negation of that number. When you pass it a positive number it returns the number as is, and the same goes for when you pass the number zero.

Math.abs(-5); // => 5
Math.abs(5); // => 5
Math.abs(0); // => 0

By using Math.abs() you are ensured to have a positive number returned to you.