javascript - Random Hex generator (only grey colors) - Stack Overflow

I found on stackoverflow this color generator :

Math.random()*0xFFFFFF<<0

It works fine. The only problem is that I'd like to generate random colors, but only of different shades of grey.

I have no idea how I could achieve something like this.

I found on stackoverflow this color generator :

Math.random()*0xFFFFFF<<0

It works fine. The only problem is that I'd like to generate random colors, but only of different shades of grey.

I have no idea how I could achieve something like this.

• javascript

Share Follow asked Mar 27, 2014 at 15:44 Romain BraunRomain Braun 3,68444 gold badges2626 silver badges4646 bronze badges 1

• Just generate a single random number between 0 and 255 and use that for the r,g and b ponent. – Matt Burland Commented Mar 27, 2014 at 15:51

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 13

var value = Math.random() * 0xFF | 0;
var grayscale = (value << 16) | (value << 8) | value;
var color = '#' + grayscale.toString(16);

color will be a random grayscale hex color value, appropriate for using in eg element.style properties.

Note: there are several ways to coerce the random floating-point number to an integer. Bitwise OR (x | 0) will usually be the fastest, as far as I know; the floor function (Math.floor(x)) is approximately the same speed, but only truncates for positive numbers (you'd have to use Math.ceil(x) for negative numbers). Bitwise operators won't work as expected for numbers that require more than 32 bits to represent, but Math.random() * 0xFF will always be in the range [0,255).

If you want to use RGB, rgb grays can be created by supplying the same number in all three arguments i.e. rgb(255,255,255) (the number must be between 0 and 255).

        function getRandomInt(min, max) {
            min = Math.ceil(min);
            max = Math.floor(max);
            return Math.floor(Math.random() * (max - min)) + min; 
        }


        var randomNumberString = String(getRandomInt(0,255));
        var color = "rgb(" + randomNumberString + "," + randomNumberString + "," + randomNumberString + ")";