How to get function name using object inside function in javascript?

In this post, You learn how to get function names from inside a function and outside a function.

The function can be created with a name called named functions as seen below.

function namedfunction() {
  // code inside the function
}

Also, functions created without a name are called anonymous functions (without a name)

var anonymousFunction = function () {
  // code inside the function
};

ES6 way to get the function name

We can get the function name using

function.name
object.constructor.name

function name property to get the function name

ECMAScript 6 introduction Function object which has name attribute to give the name of the function.

It is readonly property.

Let’s see how to get named functions.

function myfunction() {
  console.log("my function");
}
console.log(myfunction.name); //myfunction
console.log(myfunction.prototype.constructor.name); //myfunction

constructor.name property

We can also get function names using object

Let’s create an object of function.

The object has a constructor object which has a name property. This can also be invoked with the class prototype as seen below.

Here is a syntax

{function}.prototype.constructor.name
{object}.constructor.name

Here is a code to `for example get the name of the named function.

function myfunction1() {
  console.log("myfunction1"); //Person
}
var mf = new myfunction1();
console.log(myfunction1.prototype.constructor.name); //myfunction1
console.log(mf.constructor.name); //myfunction1

Here is a code for example to get the name of anonymous function

const myfunction = function () {
  console.log("my function");
};
console.log(myfunction.name); //myfunction
console.log(myfunction.prototype.constructor.name); //myfunction

How to get the running function name

We have a function in javascript running, and want to get the name of the function inside a body.

we can get the name of the function in many ways

using arguments callee

arguments.callee returns the function definition, and from that definition, gets the function name using string functions.

Here is a complete code example

function myfunction() {
  var functName = arguments.callee.toString();
  console.log(functName); // prints function definition
  functName = functName.substr("function ".length);
  functName = functName.substr(0, functName.indexOf("("));
  console.log(functName);
}
myfunction();

Another way is to get arguments.callee.name

In this example, the Function is defined and called from the outside global scope.

function myfunction1() {
  console.log(arguments.callee.name);
}
myfunction1();

How to get dynamic function names in javascript

As dynamic functions are created with different names dynamically.

Let’s create a dynamic function with a variable containing the name of the function.

Inside a function, you can access the name directly that returns the name of the function.

var dynamicfunction = "myfunction";

window[dynamicfunction] = function () {
  console.log(dynamicfunction);
};

Conclusion

You learned multiple ways to find the name of the function inside a running function and from the global scope outside.