Javascript get all function names

Function: name

The name data property of a Function instance indicates the function’s name as specified when it was created, or it may be either anonymous or » (an empty string) for functions created anonymously.

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Value

Property attributes of Function: name
Writable	no
Enumerable	no
Configurable	yes

Note: In non-standard, pre-ES2015 implementations the configurable attribute was false as well.

Description

The function’s name property can be used to identify the function in debugging tools or error messages. It has no semantic significance to the language itself.

The name property is read-only and cannot be changed by the assignment operator:

function someFunction() > someFunction.name = "otherFunction"; console.log(someFunction.name); // someFunction 

The name property is typically inferred from how the function is defined. In the following sections, we will describe the various ways in which it can be inferred.

Function declaration

The name property returns the name of a function declaration.

function doSomething() > doSomething.name; // "doSomething" 

Default-exported function declaration

An export default declaration exports the function as a declaration instead of an expression. If the declaration is anonymous, the name is «default» .

// -- someModule.js -- export default function () > // -- main.js -- import someModule from "./someModule.js"; someModule.name; // "default" 

Function constructor

Functions created with the Function() constructor have name «anonymous».

new Function().name; // "anonymous" 

Function expression

If the function expression is named, that name is used as the name property.

const someFunction = function someFunctionName() >; someFunction.name; // "someFunctionName" 

Anonymous function expressions created using the keyword function or arrow functions would have «» (an empty string) as their name.

However, such cases are rare — usually, in order to refer to the expression elsewhere, the function expression is attached to an identifier when it’s created (such as in a variable declaration). In such cases, the name can be inferred, as the following few subsections demonstrate.

One practical case where the name cannot be inferred is a function returned from another function:

function getFoo()  return () => >; > getFoo().name; // "" 

Variable declaration and method

Variables and methods can infer the name of an anonymous function from its syntactic position.

const f = function () >; const object =  someMethod: function () >, >; console.log(f.name); // "f" console.log(object.someMethod.name); // "someMethod" 

The same applies to assignment:

Initializer and default value

Functions in initializers (default values) of destructuring, default parameters, class fields, etc., will inherit the name of the bound identifier as their name .

const [f = () => >] = []; f.name; // "f" const  someMethod: m = () => > > = >; m.name; // "m" function foo(f = () => >)  console.log(f.name); > foo(); // "f" class Foo  static someMethod = () => >; > Foo.someMethod.name; // someMethod 

Shorthand method

const o =  foo() >, >; o.foo.name; // "foo"; 

Bound function

Function.prototype.bind() produces a function whose name is «bound » plus the function name.

function foo() > foo.bind(>).name; // "bound foo" 

Getter and setter

When using get and set accessor properties, «get» or «set» will appear in the function name.

const o =  get foo() >, set foo(x) >, >; const descriptor = Object.getOwnPropertyDescriptor(o, "foo"); descriptor.get.name; // "get foo" descriptor.set.name; // "set foo"; 

Class

A class’s name follows the same algorithm as function declarations and expressions.

Warning: JavaScript will set the function’s name property only if a function does not have an own property called name . However, classes’ static members will be set as own properties of the class constructor function, and thus prevent the built-in name from being applied. See an example below.

Symbol as function name

If a Symbol is used a function name and the symbol has a description, the method’s name is the description in square brackets.

const sym1 = Symbol("foo"); const sym2 = Symbol(); const o =  [sym1]() >, [sym2]() >, >; o[sym1].name; // "[foo]" o[sym2].name; // "[]" 

Private property

Private fields and private methods have the hash ( # ) as part of their names.

class Foo  #field = () => >; #method() > getNames()  console.log(this.#field.name); console.log(this.#method.name); > > new Foo().getNames(); // "#field" // "#method" 

Examples

Telling the constructor name of an object

You can use obj.constructor.name to check the «class» of an object.

function Foo() > // Or: class Foo <> const fooInstance = new Foo(); console.log(fooInstance.constructor.name); // "Foo" 

However, because static members will become own properties of the class, we can’t obtain the class name for virtually any class with a static method property name() :

class Foo  constructor() > static name() > > 

With a static name() method Foo.name no longer holds the actual class name but a reference to the name() function object. Trying to obtain the class of fooInstance via fooInstance.constructor.name won’t give us the class name at all, but instead a reference to the static class method. Example:

const fooInstance = new Foo(); console.log(fooInstance.constructor.name); // ƒ name() <> 

Due to the existence of static fields, name may not be a function either.

class Foo  static name = 123; > console.log(new Foo().constructor.name); // 123 

If a class has a static property called name , it will also become writable. The built-in definition in the absence of a custom static definition is read-only:

.name = "Hello"; console.log(Foo.name); // "Hello" if class Foo has a static "name" property, but "Foo" if not. 

Therefore you may not rely on the built-in name property to always hold a class’s name.

JavaScript compressors and minifiers

Warning: Be careful when using the name property with source-code transformations, such as those carried out by JavaScript compressors (minifiers) or obfuscators. These tools are often used as part of a JavaScript build pipeline to reduce the size of a program prior to deploying it to production. Such transformations often change a function’s name at build time.

function Foo() > const foo = new Foo(); if (foo.constructor.name === "Foo")  console.log("'foo' is an instance of 'Foo'"); > else  console.log("Oops!"); > 

function a() > const b = new a(); if (b.constructor.name === "Foo")  console.log("'foo' is an instance of 'Foo'"); > else  console.log("Oops!"); > 

In the uncompressed version, the program runs into the truthy branch and logs «‘foo’ is an instance of ‘Foo'» — whereas, in the compressed version it behaves differently, and runs into the else branch. If you rely on the name property, like in the example above, make sure your build pipeline doesn’t change function names, or don’t assume a function has a particular name.

Specifications

Browser compatibility

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See also

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This page was last modified on Apr 12, 2023 by MDN contributors.

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Источник

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 property to get the function name

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

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.

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.

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.

Источник

JavaScript — get function argument names

Giles-Whittaker

In this short article we would like to show sinmple way how to get function argument names in JavaScript.

Note: be careful, transpilation and compression may change argument names.

// ONLINE-RUNNER:browser; const functionExpression = /^(?:function(?:\s+[^\(]+)?)?\(\s*([^\)]*\s*)\)/i; const delimiterExpression = /,\s*/i; const getArgumentNames = action => < const code = action.toString(); const matching = functionExpression.exec(code); if (matching) < const group = matching[1]; return group.split(delimiterExpression); >return []; >; // Usage example: function myFunction1(arg1) < console.log('myFunction1 called. '); >const myFunction2 = function FunctionName(arg1, arg2) < console.log('FunctionName called. '); >; const myFunction3 = function(arg1, arg2, arg3) < console.log('myFunction3 called. '); >; const myFunction4 = (arg1, arg2, arg3, arg4) => < console.log('myFunction3 called. '); >; console.log(getArgumentNames(myFunction1)); console.log(getArgumentNames(myFunction2)); console.log(getArgumentNames(myFunction3)); console.log(getArgumentNames(myFunction4));

Note: above example code doesn’t wor for code with placed comments inside function declaration (e.g. function /* note . */ myFunction() < >). It is necessary to do some preprocessing to remove comments.

Источник

dfkaye / js-get-fn-name.js

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function getFnName ( fn )

fn = Object ( fn )

var F = typeof fn == ‘function’

var N = fn . name

var S = F && ( ( N && [ » , N ] ) || fn . toString ( ) . match ( / function ( [ ^ \( ] + ) / ) )

return ( ! F && ‘not a function’ ) || ( S && S [ 1 ] || ‘anonymous’ ) ;

>

console . log ( getFnName ( String ) ) ; // ‘String’

console . log ( getFnName ( function test ( ) < >) ) ; // ‘test’

console . log ( getFnName ( function ( ) < >) ) ; // ‘anonymous’

console . log ( getFnName ( function ( ) < >) ) ; // ‘anonymous’

console . log ( getFnName ( ( ) => < >) ) ; // ‘anonymous’

console . log ( getFnName ( < name : 'test' >) ) ; // ‘not a function’

console . log ( getFnName ( ‘test’ ) ) ; // ‘not a function’

console . log ( getFnName ( ) ) // ‘not a function’

console . log ( getFnName ( null ) ) // ‘not a function’

try

console . log ( getFnName ( Function ( ) ) ) ; // ‘anonymous’

> catch ( e )

console . error ( «eval() not supported» )

>

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