How to return void in JsDoc?

Question

Is there a specified way to declare a method or a function to return void in JsDoc? Currently I am in the belief that void is the default return value, and other return values must be specifically provided:

/**
 * @return {Integer} The identifier for ...
 */

Solution 1

I don't believe you have to choose from a set of types in JsDoc... you can use any type name you wish (the curly braces indicate it's a type), so you can simply do:

@return {void}

Although, this is probably more correct for JavaScript:

@return {undefined}

Solution 2

Closure Compiler

According to the documentation of Google's Closure Compiler if nothing is being returned, the @return annotation should be omitted.

If there is no return value, do not use a @return tag.

Source: https://developers.google.com/closure/compiler/docs/js-for-compiler#tags

jsdoc-toolkit

However further documentation also states that the returnType and returnDescription are optional parameters.

returnType - Optional: the type of the return value.

returnDescription - Optional: any additional description.

Source: https://code.google.com/p/jsdoc-toolkit/wiki/TagReturns

Summary

You could either leave out the return annotation or include it without any parameters.

Solution 3

Looking at the ESlint docs they use @returns {void}

Source: http://eslint.org/docs/rules/valid-jsdoc

Since I need to provide an @returns for each function to pass tests in order to push code for certain projects this is required in my case.

Solution 4

If you need to say out loud that nothing is returned, you can say that in the free-form description. This is useful to clarify situations where a user might expect something to be returned. Of course proper naming of the function and the parameters should alone make the expected return type apparent, but it might not always be possible.

/**
 * This is a funny function. Returns nothing.
 * @param {string} a joke.
 */
var funny = function (joke) {
  console.log(joke);
};

View more solutions

Comments

[Lucio Paiva]

This answer is actually better than the accepted one. If your function doesn't return a result, you shouldn't say it returns undefined as this is already implicit in Javascript and may cause confusion to whoever reads your docs.

[hellboy]

may be also @returns {void} ?

[Eugene]

What about returning null?

[BadHorsie]

@Eugene null is not necessarily the same as undefined

[Shanimal]

@return {Void} throws code inspection warning in IntelliJ IDE @return {undefined} and @return {void} does not.

[M. Eriksson]

null is never the same as undefined. When something is null, it is still defined but with no value. Undefined is, well, not defined :-)

[Aaron Mansheim]

The Ecmascript specifications list the language's types. The value returned by the void operator is undefined. The name of the type of the value undefined is Undefined, even though typeof undefined evaluates to "undefined". The name Void is not defined in Ecmascript specifications.

[Mörre]

No, I disagree and say this is not a good idea. When something is missing you don't know if it was intentional or not. By being explicit about the return type even when it's undefined you force yourself to state your intent, also good when reading it later. Just to clarify, I'm not saying one should include a useless JS statement, I'm saying one should always include a JSDoc @returns statement (I'm against useless code, but not against "useless" comments).

[GrayedFox]

IMO it makes sense to specify a return type of undefined if it is possible that your function or method returns any other value, in which case you get something like this: @returns {Array|undefined} - returns array if operation successful, otherwise returns undefined

[aljabear]

I know it's not Python, but "explicit is better than implicit"

[phoenixdown]

eslint.org/docs/rules/valid-jsdoc - per the answer below should be @returns {void} not {Void} and not {undefined}. since this is top + accepted answer, would you consider editing?

[Paul]

eslint-plugin-jsdoc gets unhappy if you leave out a @returns {void}