JAVASCRIPT

js is function

if(typeof test === "function") {
  console.log('test is a function');
}else {
  console.log('test is not a function');
}

is function javascript

// There are various ways to test if a variable is of function type
// typeof check
if(typeof test === "function"){
  // do something with function
  test()
}
// instanceof check
if(test instanceof Function){
  // do something with function
  test()
}
// call check
if(test?.call !== "undefined"){
   test.call({}, arg1, arg2);
}