Color-hash any string to a stable color

string2color.js

// DONE: Translated to XQuery
if (!String.prototype.hashCode){
    String.prototype.hashCode = function() {
      var hash = 0, i, chr, len;
      if (this.length == 0) return hash;
      for (i = 0, len = this.length; i < len; i++) {
        chr   = this.charCodeAt(i);
        hash  = ((hash << 5) - hash) + chr;
        hash |= 0; // Convert to 32bit integer
      }
      return hash;
    };
};

if (!String.prototype.pad){
    String.prototype.pad = function(length) {
      let s = this + "";
      while (s.length < length) s = "0" + s;
      return s;
    };
};

// I've been spoiled by XQuery's fn:last() function...
if (!Array.prototype.last){
    Array.prototype.last = function(){
        return this[this.length - 1];
    };
};

var hashStringToHsvColor = function(string){
    if (typeof(string) == "string") {
        var hash = string.hashCode();
        return {
            h: (hash & 0xFF0000) >> 16,
            s: (hash & 0x00FF00) >> 8,
            v: (hash & 0x0000FF)
        };
    } else {
        return {
            h: 0,
            s: 0,
            v: 0
        };
    }; 
};

/** Accepts values from 0 to 1 */
var HSVtoRGB = function(h, s, v) {
    var r, g, b, i, f, p, q, t;
    if (h && s === undefined && v === undefined) {
        s = h.s, v = h.v, h = h.h;
    }
    i = Math.floor(h * 6);
    f = h * 6 - i;
    p = v * (1 - s);
    q = v * (1 - f * s);
    t = v * (1 - (1 - f) * s);
    switch (i % 6) {
        case 0: r = v, g = t, b = p; break;
        case 1: r = q, g = v, b = p; break;
        case 2: r = p, g = v, b = t; break;
        case 3: r = p, g = q, b = v; break;
        case 4: r = t, g = p, b = v; break;
        case 5: r = v, g = p, b = q; break;
    }
    return {
        r: Math.floor(r * 255),
        g: Math.floor(g * 255),
        b: Math.floor(b * 255)
    };
};

var string2color = function(string) {
    var hsv = hashStringToHsvColor(string);
    var rgb = HSVtoRGB(hsv.h/255, hsv.s/255, hsv.v/255);
    return "#" + rgb.r.toString(16).pad(2) + rgb.g.toString(16).pad(2) + rgb.b.toString(16).pad(2);
};