//是否存在指定函数
function isExitsFunction(funcName) {
    try {
        if (typeof(eval(funcName)) == "function") {
            return true;
        }
    } catch(e) {}
    return false;
}
//是否存在指定变量
function isExitsVariable(variableName) {
    try {
        if (typeof(variableName) == "undefined") {
            //alert("value is undefined");
            return false;
        } else {
            //alert("value is true");
            return true;
        }
    } catch(e) {}
    return false;
}