html get color gradient percentage

1function pickHex(color1, color2, weight) {
2    var w1 = weight;
3    var w2 = 1 - w1;
4    var rgb = [Math.round(color1[0] * w1 + color2[0] * w2),
5        Math.round(color1[1] * w1 + color2[1] * w2),
6        Math.round(color1[2] * w1 + color2[2] * w2)];
7    return rgb;
8}