Suggestion: Iterate through Enum values

[aciccarello]

Enums currently get outputted to an object with two-way mapping of numbers. This makes it hard to iterate through the names (or values) of an enum. A method on the enum object to get the keys of the enum would allow iterating.

See this StackOverflow question for a use case of iterating. (And use of a regular expression for filtering).

Possible Solutions:

• Add a length property (for enums with default index) too limited
• Function on enum type filtering keys looking for numbers (could break with other index types)
• Add a function with the keys hard coded when compiling

Complications:

• User defined indexing
• Negative index numbers
• Proposals for other index types (Proposal: String enums #3192, Allow enums of types other than number #1206, Index signature parameter type should allow for enums #2491)

[danquirk]

I don't think this is a common enough case to emit such a helper for all enums that every TypeScript user writes.

Note that you can merge modules and enums to add methods to the enum yourself if you really do need this functionality. For example, using ES6 generators you can achieve something close to what you want:

enum E {
    A = 2,
    B = 4,
    C = 6
}

module E {
    export function* getvalues() {
        yield E.A;
        yield E.B;
        yield E.C;
    }
}

for(var i of E.getvalues()) {
    console.log(i);
}

[aciccarello]

Okay, thanks for the suggestion. I'll see if that is a suitable solution.

[Novalaina]

Seems like it would be a common use-case to me. I certainly would like that included automatically.

[bladepan]

It is a common case, for example, you may want to generate a dropdown list from enum dynamically. It is easy to implement too, just add length property to the enum.

(function (MyOptions) {
    MyOptions[MyOptions["option1"] = 0] = "option1";
    MyOptions[MyOptions["option2"] = 1] = "option2";
    MyOptions.length = 2;
})(MyOptions || (MyOptions = {}));

[npiv]

I don't understand the argumentation to not include this at all. Too complex maybe, but not a common use case...

What other language has enums and no way to iterate over them?

[RyanCavanaugh]

no way to iterate over them?

You can iterate over them. See http://stackoverflow.com/a/18112474/1704166 .

[npiv]

@RyanCavanaugh

Thank you that does work. My mistake - I misunderstood this issue.

[alamothe]

@danquirk Can't compiler just emit the same code?

It is really sad it's not supported, as every other language with enums have the functionality

[omerman]

@danquirk I agree with @alamothe so much that I'm leaving this comment saying just that.

[RyanCavanaugh]

Please don't show up with noise comments.

[saenglert]

Well, generally how else are people able to show their support but by making some noise for the cause?

This issue is rank 4 on DuckDuckGo and 3 on Google when searching "typescript iterate enum" (which is how I got here as well). I guess wanting to iterate over enums is not an uncommon use case after all and both solutions that were brought up in here are essentially workarounds and quite bulky.