/**
 * Created by laixiangran on 2015/12/12.
 * String擴展
 */
(function() {

    // 十六進位顏色值的正則表達式
    var reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;

    // RGB顏色轉換為16進位
    if (typeof String.prototype.rgbToHex != "function") {
        String.prototype.rgbToHex = function() {
            var that = this;
            if (/^(rgb|RGB)/.test(that)) {
                var aColor = that.replace(/(?:\(|\)|rgb|RGB)*/g,"").split(",");
                var strHex = "#";
                for (var i=0; i<aColor.length; i++) {
                    var hex = Number(aColor[i]).toString(16);
                    if (hex === "0") {
                        hex += hex;
                    }
                    strHex += hex;
                }
                if (strHex.length !== 7) {
                    strHex = that;
                }
                return strHex;
            }else if (reg.test(that)) {
                var aNum = that.replace(/#/,"").split("");
                if (aNum.length === 6){
                    return that;
                }else if (aNum.length === 3) {
                    var numHex = "#";
                    for (var j=0; j<aNum.length; j++) {
                        numHex += (aNum[j]+aNum[j]);
                    }
                    return numHex;
                }
            }else{
                return that;
            }
        };
    }

    // 16進位顏色轉為RGB格式
    if (typeof String.prototype.hexToRgb != "function") {
        String.prototype.hexToRgb = function() {
            var sColor = this.toLowerCase();
            if (sColor && reg.test(sColor)) {
                if (sColor.length === 4) {
                    var sColorNew = "#";
                    for (var i = 1; i < 4; i++) {
                        sColorNew += sColor.slice(i,i+1).concat(sColor.slice(i,i+1));
                    }
                    sColor = sColorNew;
                }
                // 處理六位的顏色值
                var sColorChange = [];
                for (var j=1; j<7; j+=2) {
                    sColorChange.push(parseInt("0x"+sColor.slice(j,j+2)));
                }
                return "RGB(" + sColorChange.join(",") + ")";
            }else{
                return sColor;
            }
        };
    }

    // 移除字元串首尾空白
    if (typeof String.prototype.trim != "function") {
        String.prototype.trim = function() {
            return this.replace(/^\s+|\s+$/g, "");
        };
    }
}());

參考

http://www.cnblogs.com/rubylouvre/archive/2009/09/18/1568794.html

http://www.cnblogs.com/rubylouvre/archive/2009/11/15/1603405.html