Function.displayName

function doSomething() {}

console.log(doSomething.displayName); // "undefined"

var popup = function (content) {
  console.log(content);
};

popup.displayName = "Show Popup";

console.log(popup.displayName); // "Show Popup"

var object = {
  someMethod: function () {},
};

object.someMethod.displayName = "someMethod";

console.log(object.someMethod.displayName); // logs "someMethod"

try {
  someMethod;
} catch (e) {
  console.log(e);
}
// ReferenceError: someMethod is not defined

var object = {
  // anonymous
  someMethod: function (value) {
    arguments.callee.displayName = "someMethod (" + value + ")";
  },
};

console.log(object.someMethod.displayName); // "undefined"

object.someMethod("123");
console.log(object.someMethod.displayName); // "someMethod (123)"

var a = function () {};
a.displayName = "My Function";

a; // "function My Function()"