枚举的打字稿类型别名

Question

I have this in my typings file:

declare namespace Somatic {
    enum PropType {
        html,
        object,
        css
    }
}

In another file index.ts, I have a shorter alias for this enum as:

type PropType = Somatic.PropType;

Then I want to use the aliased enum type in a switch statement:

switch (propType) {
    case PropType.html:
        break;
    .
    .
    .
    }

But Typescript does not recognize the aliased enum type values. What is wrong here?

Answer 1

You should use import keyword instead of type :

import PropType = Somatic.PropType;

More info on import alias declarations here .

** This syntax won't work if you're using babel-plugin-transform-typescript because this is typescript only form of import. Generally using namespaces is not recommended.

Answer 2

In typescript, an enum is both a type and a map. You should alias the type and the map separately:

type PropTypeEnum = Somatic.PropType;
const PropType = Somatic.PropType;

Answer 3

Basically, a definition file is simply declaring the type of existing other code. Enums in TypeScript are actually numbers and more than likely the existing code you're building on top of doesn't use actual numbers. A better implementation would probably be to just switch strings;