How can I use enum values as index of array

Question

I try to use enum value as index of array but it gives me an error.

export class Color {
    static RED = 0;
    static BLUE = 1;
    static GREEN = 2;
}

let x = ['warning', 'info', 'success'];
let anotherVariable = x[Color.RED]; <---- Error: Type 'Color' cannot be used as an index type.

I tried Number() and parseInt to convert to number but it does not work.

Is there any way that I can use Enum values as an index?

Thats not an enum. And Color.RED is not an instance of Color. — tkausl
– tkausl, Commented Jul 8, 2019 at 7:35
Works for me in plain JS in Chrome if I remove the export keyword — mplungjan
– mplungjan, Commented Jul 8, 2019 at 7:40
@mplungjan same here. But not in firefox - it reports that fields are not yet supported. — VLAZ
– VLAZ, Commented Jul 8, 2019 at 7:40
It only shows this error when you have x[Color] instead of x[Color.RED] Typescript Playground — adiga
– adiga, Commented Jul 8, 2019 at 7:51

claasic · Accepted Answer · 2019-07-08 07:43:21Z

2

To create an Enum we create a const frozen object. For the difference and why see the below quote:

const applies to bindings ("variables"). It creates an immutable binding, i.e. you cannot assign a new value to the binding.

Object.freeze works on values, and more specifically, object values. It makes an object immutable, i.e. you cannot change its properties.

From: https://stackoverflow.com/a/33128023/9758920

Afterwards we can still access the keys and values like with a normal object.

// https://stackoverflow.com/questions/287903/what-is-the-preferred-syntax-for-defining-enums-in-javascript
const COLORS = Object.freeze({"RED":0, "BLUE":1, "GREEN":2})

let x = ['warning', 'info', 'success'];
let anotherVariable = x[COLORS.RED]; 

console.log(anotherVariable)

Also check out: https://stackoverflow.com/a/49309248/9758920

edited Jul 8, 2019 at 7:43

answered Jul 8, 2019 at 7:40

claasic

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2 Comments

adiga Over a year ago

This doesn't answer why the posted code is throwing the error

claasic Over a year ago

As seen from the comments: very likely a browser support problem.

Oyewole A. Samuel · Accepted Answer · 2019-07-08 07:40:05Z

0

Try this.

    let color = {
        RED : 0,
        BLUE : 1,
        GREEN : 2
    }

    module.exports = color

    let x = ['warning', 'info', 'success'];
    let anotherVariable = x[color.RED];

answered Jul 8, 2019 at 7:40

Oyewole A. Samuel

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