---
title: "Signature (functions) - Glossary | MDN"
chunk: 1/3
source: "https://developer.mozilla.org/en-US/docs/Glossary/Signature/Function"
category: "reference"
tags: "web, html, css, javascript, documentation"
date_saved: "2026-05-05T05:45:18.977541+00:00"
instance: "kb-cron"
---

  * [Skip to main content](https://developer.mozilla.org/en-US/docs/Glossary/Signature/Function#content)
  * [Skip to search](https://developer.mozilla.org/en-US/docs/Glossary/Signature/Function#search)

[ MDN ](https://developer.mozilla.org/en-US/)
HTML
[HTML: Markup language](https://developer.mozilla.org/en-US/docs/Web/HTML) 

HTML reference
    
  * [Elements](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements)
  * [Global attributes](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Global_attributes)
  * [Attributes](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Attributes)
  * [See all…](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference "See all HTML references")

HTML guides
    
  * [Responsive images](https://developer.mozilla.org/en-US/docs/Web/HTML/Guides/Responsive_images)
  * [HTML cheatsheet](https://developer.mozilla.org/en-US/docs/Web/HTML/Guides/Cheatsheet)
  * [Date & time formats](https://developer.mozilla.org/en-US/docs/Web/HTML/Guides/Date_and_time_formats)
  * [See all…](https://developer.mozilla.org/en-US/docs/Web/HTML/Guides "See all HTML guides")

Markup languages
    
  * [SVG](https://developer.mozilla.org/en-US/docs/Web/SVG)
  * [MathML](https://developer.mozilla.org/en-US/docs/Web/MathML)
  * [XML](https://developer.mozilla.org/en-US/docs/Web/XML)

CSS
[CSS: Styling language](https://developer.mozilla.org/en-US/docs/Web/CSS) 

CSS reference
    
  * [Properties](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Properties)
  * [Selectors](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Selectors)
  * [At-rules](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/At-rules)
  * [Values](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference/Values)
  * [See all…](https://developer.mozilla.org/en-US/docs/Web/CSS/Reference "See all CSS references")

CSS guides
    
  * [Box model](https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Box_model/Introduction)
  * [Animations](https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Animations/Using)
  * [Flexbox](https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Flexible_box_layout/Basic_concepts)
  * [Colors](https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Colors/Applying_color)
  * [See all…](https://developer.mozilla.org/en-US/docs/Web/CSS/Guides "See all CSS guides")

Layout cookbook
    
  * [Column layouts](https://developer.mozilla.org/en-US/docs/Web/CSS/How_to/Layout_cookbook/Column_layouts)
  * [Centering an element](https://developer.mozilla.org/en-US/docs/Web/CSS/How_to/Layout_cookbook/Center_an_element)
  * [Card component](https://developer.mozilla.org/en-US/docs/Web/CSS/How_to/Layout_cookbook/Card)
  * [See all…](https://developer.mozilla.org/en-US/docs/Web/CSS/How_to/Layout_cookbook)

JavaScriptJS
[JavaScript: Scripting language](https://developer.mozilla.org/en-US/docs/Web/JavaScript) 

JS reference
    
  * [Standard built-in objects](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects)
  * [Expressions & operators](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators)
  * [Statements & declarations](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements)
  * [Functions](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions)
  * [See all…](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference "See all JavaScript references")

JS guides
    
  * [Control flow & error handing](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Control_flow_and_error_handling)
  * [Loops and iteration](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Loops_and_iteration)
  * [Working with objects](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_objects)
  * [Using classes](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Using_classes)
  * [See all…](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide "See all JavaScript guides")

Web APIs
[Web APIs: Programming interfaces](https://developer.mozilla.org/en-US/docs/Web/API) 

Web API reference
    
  * [File system API](https://developer.mozilla.org/en-US/docs/Web/API/File_System_API)
  * [Fetch API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API)
  * [Geolocation API](https://developer.mozilla.org/en-US/docs/Web/API/Geolocation_API)
  * [HTML DOM API](https://developer.mozilla.org/en-US/docs/Web/API/HTML_DOM_API)
  * [Push API](https://developer.mozilla.org/en-US/docs/Web/API/Push_API)
  * [Service worker API](https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API)
  * [See all…](https://developer.mozilla.org/en-US/docs/Web/API "See all Web API guides")

Web API guides
    
  * [Using the Web animation API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Animations_API/Using_the_Web_Animations_API)
  * [Using the Fetch API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch)
  * [Working with the History API](https://developer.mozilla.org/en-US/docs/Web/API/History_API/Working_with_the_History_API)
  * [Using the Web speech API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Speech_API/Using_the_Web_Speech_API)
  * [Using web workers](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Using_web_workers)

All
[All web technology](https://developer.mozilla.org/en-US/docs/Web) 

Technologies
    
  * [Accessibility](https://developer.mozilla.org/en-US/docs/Web/Accessibility)
  * [HTTP](https://developer.mozilla.org/en-US/docs/Web/HTTP)
  * [URI](https://developer.mozilla.org/en-US/docs/Web/URI)
  * [Web extensions](https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions)
  * [WebAssembly](https://developer.mozilla.org/en-US/docs/WebAssembly)
  * [WebDriver](https://developer.mozilla.org/en-US/docs/Web/WebDriver)
  * [See all…](https://developer.mozilla.org/en-US/docs/Web "See all web technology references")

Topics
    
  * [Media](https://developer.mozilla.org/en-US/docs/Web/Media)
  * [Performance](https://developer.mozilla.org/en-US/docs/Web/Performance)
  * [Privacy](https://developer.mozilla.org/en-US/docs/Web/Privacy)
  * [Security](https://developer.mozilla.org/en-US/docs/Web/Security)
  * [Progressive web apps](https://developer.mozilla.org/en-US/docs/Web/Progressive_web_apps)

Learn
[Learn web development](https://developer.mozilla.org/en-US/docs/Learn_web_development) 

Frontend developer course
    
  * [Getting started modules](https://developer.mozilla.org/en-US/docs/Learn_web_development/Getting_started)
  * [Core modules](https://developer.mozilla.org/en-US/docs/Learn_web_development/Core)
  * [MDN Curriculum](https://developer.mozilla.org/en-US/curriculum/)
  * [Check out the video course from Scrimba, our partner](https://scrimba.com/frontend-path-c0j?via=mdn-learn-navbar)

Learn HTML
    
  * [Structuring content with HTML module](https://developer.mozilla.org/en-US/docs/Learn_web_development/Core/Structuring_content)

Learn CSS
    
  * [CSS styling basics module](https://developer.mozilla.org/en-US/docs/Learn_web_development/Core/Styling_basics)
  * [CSS layout module](https://developer.mozilla.org/en-US/docs/Learn_web_development/Core/CSS_layout)

Learn JavaScript
    
  * [Dynamic scripting with JavaScript module](https://developer.mozilla.org/en-US/docs/Learn_web_development/Core/Scripting)

Tools
Discover our tools 
  * [Playground](https://developer.mozilla.org/en-US/play)
  * [HTTP Observatory](https://developer.mozilla.org/en-US/observatory)

  * [Border-image generator](https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Backgrounds_and_borders/Border-image_generator)
  * [Border-radius generator](https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Backgrounds_and_borders/Border-radius_generator)
  * [Box-shadow generator](https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Backgrounds_and_borders/Box-shadow_generator)
  * [Color format converter](https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Colors/Color_format_converter)
  * [Color mixer](https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Colors/Color_mixer)
  * [Shape generator](https://developer.mozilla.org/en-US/docs/Web/CSS/Guides/Shapes/Shape_generator)

About
Get to know MDN better 
  * [About MDN](https://developer.mozilla.org/en-US/about)
  * [Advertise with us](https://developer.mozilla.org/en-US/advertising)

  * [Community](https://developer.mozilla.org/en-US/community)
  * [MDN on GitHub](https://github.com/mdn)

[Blog](https://developer.mozilla.org/en-US/blog/)
  1. [Glossary](https://developer.mozilla.org/en-US/docs/Glossary)
  2. [Signature](https://developer.mozilla.org/en-US/docs/Glossary/Signature)
  3. [Signature (functions)](https://developer.mozilla.org/en-US/docs/Glossary/Signature/Function)

# Signature (functions)
A **function signature** (or _type_ signature, or _method_ signature) defines input and output of [functions](https://developer.mozilla.org/en-US/docs/Glossary/Function) or [methods](https://developer.mozilla.org/en-US/docs/Glossary/Method).
A signature can include:
  * [parameters](https://developer.mozilla.org/en-US/docs/Glossary/Parameter) and their [types](https://developer.mozilla.org/en-US/docs/Glossary/Type)
  * a return value and type
  * [exceptions](https://developer.mozilla.org/en-US/docs/Glossary/Exception) that might be thrown or passed back
  * information about the availability of the method in an [object-oriented](https://developer.mozilla.org/en-US/docs/Glossary/OOP) program (such as the keywords `public`, `static`, or `prototype`).

## In this article
  * [In depth](https://developer.mozilla.org/en-US/docs/Glossary/Signature/Function#in_depth)
  * [See also](https://developer.mozilla.org/en-US/docs/Glossary/Signature/Function#see_also)

##  [In depth](https://developer.mozilla.org/en-US/docs/Glossary/Signature/Function#in_depth)
###  [Signatures in JavaScript](https://developer.mozilla.org/en-US/docs/Glossary/Signature/Function#signatures_in_javascript)
[JavaScript](https://developer.mozilla.org/en-US/docs/Glossary/JavaScript) is a _loosely typed_ or a _dynamic_ language. That means you don't have to declare the type of a variable ahead of time. The type will get determined automatically while the program is being processed. A signature in JavaScript can still give you some information about the method:
  * The method is installed on an [object](https://developer.mozilla.org/en-US/docs/Glossary/Object) called `MyObject`.
  * The method is installed on the `prototype` of `MyObject` (thus it is an [instance method](https://developer.mozilla.org/en-US/docs/Glossary/Method)) as opposed to being a [static method](https://developer.mozilla.org/en-US/docs/Glossary/Static_method).
  * The name of the method is `myFunction`.
  * The method accepts one parameter, which is called `value` and is not further defined.

###  [Signatures in Java](https://developer.mozilla.org/en-US/docs/Glossary/Signature/Function#signatures_in_java)
In [Java](https://developer.mozilla.org/en-US/docs/Glossary/Java), signatures are used to identify methods and classes at the level of the virtual machine code. You have to declare types of variables in your code in order to be able to run the Java code. Java is _strictly typed_ and will check any parameters at compilation time if they are correct.
  * The `public` keyword is an access modifier and indicates that this method can be called by any object.
  * The `static` keyword indicates that this method is a class method as opposed to being an instance method.
  * The `void` keyword indicates that this method has no return value.
  * The name of the method is `main`.
  * The method accepts one parameter of type String Array. It is named `args`.

##  [See also](https://developer.mozilla.org/en-US/docs/Glossary/Signature/Function#see_also)
  * [Java internal type signatures](https://en.wikipedia.org/wiki/Type_signature#Java) on Wikipedia