js 相对路径转为绝对路径

//将相对路径转为绝对路径function getPath(relativePath, absolutePath) {    var reg = new RegExp("\\.\\./", "g");    var uplayCount = 0; // 相对路径中返回上层的次数。    var m = relativePath.match(reg);    if (m) uplayCount = m.length;    var lastIndex = absolutePath.length - 1;    var subString = absolutePath.substr(0, lastIndex + 1)    for (var i = 0; i <= uplayCount; i++) {        lastIndex = subString.lastIndexOf("/", lastIndex);        subString = subString.substr(0, lastIndex)    }    return subString + "/" + relativePath.replace(reg, "");}