How to generate random grey colors in javascript

Question

I have a function and would like to generate only grey colors. How can I do this with the code below? I'm pretty new to javascript! I'd appreciate any help. I'm using Paper.js

 function onMouseDown(event) {
        path = new Path();
        path.fillColor = {
            hue: Math.random() * 360,
            //saturation: 0,
            //brightness: 0.5
        };

        path.add(event.point);
    }

Answer 1

Since the example you provide accepts HSB colours you can simply generate a random brightness value. The saturation should be 0 (fully desaturated) and the hue can also be 0 as it is redundant.

The Brightness value should be a number between 0 an 1. Since you want grey specifically you may want to get a value back that's neither too dark or too light. We can make a little method to return a random number between two values.

function getRandomInRange(min, max) {
  return Math.random() * (max - min) + min;
}

So in you code you would use it like this:

function onMouseDown(event) {
    path = new Path();
    path.fillColor = {
        hue: 0, 
        saturation: 0,
        brightness: getRandomInRange(0.2, 0.8)
    };

    path.add(event.point);
}

Update

Paper.js has a Color constructor specifically for greyscale that would also be appropriate to use here. It takes a number from 0 - 1 (where 0 is black) so the getRandomInRange will work equally well here:

path.fillColor = new Color(getRandomInRange(0.2, 0.8)); //a random grey