How to document a string type in jsdoc with limited possible values

117
votes

I am having a function that accepts one string parameter. This parameter can have only one of a few defined possible values. What is the best way to document the same? Should shapeType be defined as enum or TypeDef or something else?

Shape.prototype.create = function (shapeType) {
    // shapeType can be "rect", "circle" or "ellipse"...
    this.type = shapeType;
};

Shape.prototype.getType = function (shapeType) {
    // shapeType can be "rect", "circle" or "ellipse"...
    return this.type;
};

The second part of the problem is that the possible values of shapeType is not known in the file that defines shapeType as whatever you suggest. There are multiple files contributed by several developers who might add to the possible values of shapeType.

PS: Am using jsdoc3

5
google-closure-compilergoogle-closurejsdoccode-documentation
The multiple files problem makes this difficult. I usually see an enum for the definition and a union for the function parameter: ShapeType|string. However enums don't support adding subtypes after declaration in Closure-compiler. - Chad Killingsworth
@ChadKillingsworth I see what you mean. I am stuck at a point where I want to define a set of properties (lets say an object that goes as construction parameter of a class). It is well and good had all properties of the construction was defined at one location. Unfortunately, my code has a number of modules contributing to that construction properties. Doing something like a mixin or subclassing the propertied would be going overboard! As such, if I can simply inject to a property list definition it would be great. - Shamasis Bhattacharya
Another similar issue that I am facing, but with distributed property listing is stackoverflow.com/questions/19113571/… - Shamasis Bhattacharya
All solutions below force us to create an Enum. There is an active feature request at GitHub to make this process much easier: github.com/jsdoc3/jsdoc/issues/629. So anybody who likes it should probably bump it. - B12Toaster

5 Answers

148
votes

As of late 2014 in jsdoc3 you have the possibility to write:

/**
 * @param {('rect'|'circle'|'ellipse')} shapeType - The allowed type of the shape
 */
Shape.prototype.getType = function (shapeType) {
  return this.type;
};

Of course this will not be as reusable as a dedicated enum but in many cases a dummy enum is an overkill if it is only used by one function.

See also: https://github.com/jsdoc3/jsdoc/issues/629#issue-31314808

46
votes

What about:

/**
 * @typedef {"keyvalue" | "bar" | "timeseries" | "pie" | "table"} MetricFormat
 */

/**
 * @param format {MetricFormat}
 */
export function fetchMetric(format) {
    return fetch(`/matric}`, format);
}

enter image description here

31
votes

How about declaring a dummy enum:

/**
 * Enum string values.
 * @enum {string}
 */
Enumeration = {
    ONE: "The number one",
    TWO: "A second number"
};

/**
 * Sample.
 * @param {Enumeration} a one of the enumeration values.
 */
Bar.prototype.sample = function(a) {};


b = new Bar();

bar.sample(Enumeration.ONE)

You need to at least declare the enum to JSDOC, for this, though. But the code is clean and you get auto-completion in WebStorm.

The multiple files problem though cannot be solved this way.

10
votes

I don't think there's a formal way of writing allowed values in JSDoc.

You certainly can write something like @param {String('up'|'down'|'left'|'right')} like user b12toaster mentioned.

enter image description here

But, by taking reference from APIDocjs, here's what I use for writing constrained values, aka allowedValues.

/**
 * Set the arrow position of the tooltip
 * @param {String='up','down','left','right'} position pointer position
 */
setPosition(position='left'){
  // YOUR OWN CODE
}

Oh yeah, I'm using ES6.

0
votes

This is how the Closure Compiler supports it: you can use "@enum" to define a restricted type. You don't actually have to define the values in enum definition. For instance, I might define an "integer" type like:

/** @enum {number} */
var Int = {};

/** @return {Int} */
function toInt(val) {
  return /** @type {Int} */ (val|0);
}

Int is generally assignable to "number" (it is a number) but "number" is not assignable to "Int" without some coercion (a cast).