Javascript method to determine whether a function exists_javascript skills

Copy code The code is as follows:

window.onload=function(){
try{

if(test&&typeof(test)=="function"){
test();
}else{
alert("Function that does not exist");
}
}catch(e){
}
}
function test(){
alert("Function execution...");
}

If not If it exists, an exception will be thrown, so try...catch must be added.