How can I loop through enum values for display in radio buttons?

Anthony Brenelière picture Anthony Brenelière · Sep 7, 2016 · Viewed 202.3k times · Source

What is the proper way to loop through literals of an enum in TypeScript?

(I am currently using TypeScript 1.8.1.)

I've got the following enum:

export enum MotifIntervention {
    Intrusion,
    Identification,
    AbsenceTest,
    Autre
}

export class InterventionDetails implements OnInit
{
    constructor(private interService: InterventionService)
    {
        let i:number = 0;
        for (let motif in MotifIntervention) {
            console.log(motif);
        }
    }

The result displayed is a list

0
1
2
3
Intrusion,
Identification,
AbsenceTest,
Autre

I do want only four iterations in the loop as there are only four elements in the enum. I don't want to have 0 1 2 and 3 that seem to be index numbers of the enum.

Answer

Nitzan Tomer picture Nitzan Tomer · Sep 7, 2016

Two options:

for (let item in MotifIntervention) {
    if (isNaN(Number(item))) {
        console.log(item);
    }
}

Or

Object.keys(MotifIntervention).filter(key => !isNaN(Number(MotifIntervention[key])));

(code in playground)


Edit

String enums look different than regular ones, for example:

enum MyEnum {
    A = "a",
    B = "b",
    C = "c"
}

Compiles into:

var MyEnum;
(function (MyEnum) {
    MyEnum["A"] = "a";
    MyEnum["B"] = "b";
    MyEnum["C"] = "c";
})(MyEnum || (MyEnum = {}));

Which just gives you this object:

{
    A: "a",
    B: "b",
    C: "c"
}

You can get all the keys (["A", "B", "C"]) like this:

Object.keys(MyEnum);

And the values (["a", "b", "c"]):

Object.keys(MyEnum).map(key => MyEnum[key])

Or using Object.values():

Object.values(MyEnum)