js get list of own static properties

Question

I have a class with static properties and I want to get a list of all property values:

class TimeRange {
    static ALL = 'all time'
    static MONTH = 'month'
    static WEEK = 'week'
    static DAY = 'day'
}

Now I want to get: ['all time', 'month', 'week', 'day']

@Chris There are no [`static`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/static) properties in JavaScript (_yet_): _"The static keyword defines a static **method** for a class."_ — Andreas, Mar 26 '18 at 15:38
Static properties are a feature proposal and can be used via Babel. — Pointy, Mar 26 '18 at 15:39
@Andreas Yes, sry. I assumed that the syntax would be the same for ES 2016 — Chris, Mar 26 '18 at 15:40

ethan.roday · Accepted Answer · 2018-03-26T16:12:00.333

What's your use case here? If you're looking for a way to have some properties that you can iterate through but also refer to by key, then you can just use a normal object:

const timeRanges = {
  ALL: 'all time',
  MONTH: 'month',
  WEEK: 'week',
  DAY: 'day'
}
timeRanges.ALL; // 'all time'
timeRanges.MINUTE; // not allowed
Object.keys(timeRanges).map(key => timeRanges[key]); // ['all time', 'month', 'week', 'day']

Classes are not really designed to have their properties iterated through. However, if they absolutely must be in a class, you could turn them into instance properties follow the method outlined here:

class TimeRange {
  ALL = 'all time'
  MONTH = 'month'
  WEEK = 'week'
  DAY = 'day'
}
Object.getOwnPropertyNames(new TimeRange()); // ['all time', 'month', 'week', 'day']

That's somewhat of an anti-pattern, though.

One final option you might consider would be to use a string enum:

enum TimeRange {
  ALL = 'all time',
  MONTH = 'month',
  WEEK = 'week',
  DAY = 'day'
}
Object.keys(TimeRange).map(key => TimeRange[key]); // ['all time', 'month', 'week', 'day']

(To clarify, I'm assuming you're using Typescript here based on the tags in the question. If you're not, then the comments on your original question stand. You could still use options 1 and 2 that I suggest here, but obviously without the type checking benefits.)

One use case which I'm currently struggling with is having the individual properties depend on one another. The example is I'm building a Class that has static members that build a store of API endpoints. For example, I have "/api1/", "/api2/" as two static members, and later, extensions of those endpoints are additional static members. You can't have these types of self references if you use an enum or an object, correct? — Adam P., Aug 21 '21 at 14:08
@AdamP. I think you're probably better off asking this as a separate question and outlining your situation in some more detail (preferably with an example) - it's hard to know what the right approach is given your comment. — ethan.roday, Aug 23 '21 at 00:26

js get list of own static properties

1 Answers1