RGB to HSV color in javascript? [closed]

Here is a standalone function:

function rgb2hsv (r, g, b) {
    let rabs, gabs, babs, rr, gg, bb, h, s, v, diff, diffc, percentRoundFn;
    rabs = r / 255;
    gabs = g / 255;
    babs = b / 255;
    v = Math.max(rabs, gabs, babs),
    diff = v - Math.min(rabs, gabs, babs);
    diffc = c => (v - c) / 6 / diff + 1 / 2;
    percentRoundFn = num => Math.round(num * 100) / 100;
    if (diff == 0) {
        h = s = 0;
    } else {
        s = diff / v;
        rr = diffc(rabs);
        gg = diffc(gabs);
        bb = diffc(babs);

        if (rabs === v) {
            h = bb - gg;
        } else if (gabs === v) {
            h = (1 / 3) + rr - bb;
        } else if (babs === v) {
            h = (2 / 3) + gg - rr;
        }
        if (h < 0) {
            h += 1;
        }else if (h > 1) {
            h -= 1;
        }
    }
    return {
        h: Math.round(h * 360),
        s: percentRoundFn(s * 100),
        v: percentRoundFn(v * 100)
    };
}

And how to use it:

console.log( rgb2hsv(60, 120, 180) );
// {h: 210, s: 66.67, v: 70.59}