// My function does X and Y.
// @params {object} parameters An object containing the parameters
// @params {function} callback The callback function
function(parameters, callback) {
}
But how do I describe how the parameters object should be structured? For example it should be something like:
{
setting1 : 123, // (required, integer)
setting2 : 'asdf' // (optional, string)
}
From the @param wiki page:
If a parameter is expected to have a particular property, you can document that immediately after the @param tag for that parameter, like so:
/**
* @param userInfo Information about the user.
* @param userInfo.name The name of the user.
* @param userInfo.email The email of the user.
*/
function logIn(userInfo) {
doLogIn(userInfo.name, userInfo.email);
}
There used to be a @config tag which immediately followed the corresponding @param, but it appears to have been deprecated (example here).
By now there are 4 different ways to document objects as parameters/types. Each has its own uses. Only 3 of them can be used to document return values, though.
For objects with a known set of properties (Variant A)
/**
* @param {{a: number, b: string, c}} myObj description
*/
This syntax is ideal for objects that are used only as parameters for this function and don't require further description of each property.
It can be used for @returns as well.
For objects with a known set of properties (Variant B)
Very useful is the parameters with properties syntax:
/**
* @param {Object} myObj description
* @param {number} myObj.a description
* @param {string} myObj.b description
* @param {} myObj.c description
*/
This syntax is ideal for objects that are used only as parameters for this function and that require further description of each property.
This can not be used for @returns.
For objects that will be used at more than one point in source
In this case a @typedef comes in very handy. You can define the type at one point in your source and use it as a type for @param or @returns or other JSDoc tags that can make use of a type.
/**
* @typedef {Object} Person
* @property {string} name how the person is called
* @property {number} age how many years the person lived
*/
You can then use this in a @param tag:
/**
* @param {Person} p - Description of p
*/
Or in a @returns:
/**
* @returns {Person} Description
*/
For objects whose values are all the same type
/**
* @param {Object.<string, number>} dict
*/
The first type (string) documents the type of the keys which in JavaScript is always a string or at least will always be coerced to a string. The second type (number) is the type of the value; this can be any type.
This syntax can be used for @returns as well.
Resources
Useful information about documenting types can be found here:
https://jsdoc.app/tags-type.html
PS:
to document an optional value you can use []:
/**
* @param {number} [opt_number] this number is optional
*/
or:
/**
* @param {number|undefined} opt_number this number is optional
*/
I see that there is already an answer about the @return tag, but I want to give more details about it.
First of all, the official JSDoc 3 documentation doesn't give us any examples about the @return for a custom object. Please see https://jsdoc.app/tags-returns.html. Now, let's see what we can do until some standard will appear.
Function returns object where keys are dynamically generated. Example: {1: 'Pete', 2: 'Mary', 3: 'John'}. Usually, we iterate over this object with the help of for(var key in obj){...}.
Possible JSDoc according to https://google.github.io/styleguide/javascriptguide.xml#JsTypes
/**
* @return {Object.<number, string>}
*/
function getTmpObject() {
var result = {}
for (var i = 10; i >= 0; i--) {
result[i * 3] = 'someValue' + i;
}
return result
}
Function returns object where keys are known constants. Example: {id: 1, title: 'Hello world', type: 'LEARN', children: {...}}. We can easily access properties of this object: object.id.
Possible JSDoc according to https://groups.google.com/forum/#!topic/jsdoc-users/TMvUedK9tC4
Fake It.
/**
* Generate a point.
*
* @returns {Object} point - The point generated by the factory.
* @returns {number} point.x - The x coordinate.
* @returns {number} point.y - The y coordinate.
*/
var pointFactory = function (x, y) {
return {
x:x,
y:y
}
}
The Full Monty.
/**
@class generatedPoint
@private
@type {Object}
@property {number} x The x coordinate.
@property {number} y The y coordinate.
*/
function generatedPoint(x, y) {
return {
x:x,
y:y
};
}
/**
* Generate a point.
*
* @returns {generatedPoint} The point generated by the factory.
*/
var pointFactory = function (x, y) {
return new generatedPoint(x, y);
}
Define a type.
/**
@typedef generatedPoint
@type {Object}
@property {number} x The x coordinate.
@property {number} y The y coordinate.
*/
/**
* Generate a point.
*
* @returns {generatedPoint} The point generated by the factory.
*/
var pointFactory = function (x, y) {
return {
x:x,
y:y
}
}
According to https://google.github.io/styleguide/javascriptguide.xml#JsTypes
The record type.
/**
* @return {{myNum: number, myObject}}
* An anonymous type with the given type members.
*/
function getTmpObject() {
return {
myNum: 2,
myObject: 0 || undefined || {}
}
}
For @return tag use {{field1: Number, field2: String}}, see: http://wiki.servoy.com/display/public/DOCS/Annotating+JavaScript+using+JSDoc
If a parameter is expected to have a specific property, you can document that property by providing an additional @param tag. For example, if an employee parameter is expected to have name and department properties, you can document it as follows:
/**
* Assign the project to a list of employees.
* @param {Object[]} employees - The employees who are responsible for the project.
* @param {string} employees[].name - The name of an employee.
* @param {string} employees[].department - The employee's department.
*/
function(employees) {
// ...
}
If a parameter is destructured without an explicit name, you can give the object an appropriate one and document its properties.
/**
* Assign the project to an employee.
* @param {Object} employee - The employee who is responsible for the project.
* @param {string} employee.name - The name of the employee.
* @param {string} employee.department - The employee's department.
*/
Project.prototype.assign = function({ name, department }) {
// ...
};
Source: JSDoc
There's a new @config tag for these cases. They link to the preceding @param.
/** My function does X and Y.
@params {object} parameters An object containing the parameters
@config {integer} setting1 A required setting.
@config {string} [setting2] An optional setting.
@params {MyClass~FuncCallback} callback The callback function
*/
function(parameters, callback) {
// ...
};
/**
* This callback is displayed as part of the MyClass class.
* @callback MyClass~FuncCallback
* @param {number} responseCode
* @param {string} responseMessage
*/
