//是否存在指定函數 function isExitsFunction(funcName) {  try {    if (typeof(eval(funcName)) == "function") {      return true;    }  } catch(e) {}  return false;}//是否存在指定變量 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;}