js simple sample code to determine whether js functions and variables exist_javascript skills

Copy code The code is as follows:

//Whether the specified function exists
function isExitsFunction(funcName) {
try {
if (typeof(eval(funcName)) == "function") {
return true;
}
} catch(e) {}
return false;
}
//Whether the specified variable exists
function isExitsVariable(variableName) {
try {
if (typeof(variableName) == "undefined") {
//alert( "value is undefined");
              return false; ) {}
return false;
}