core code
//Whether the specified function function exists isExitsFunction(funcName) { try { if (typeof(eval(funcName)) == "function") { return true; } } catch(e) {} return false;}//Whether the specified function exists Variable 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;}For more judgment, please refer to this article: //www.VeVB.COm/article/67551.htm