StringEnum for Typescript

Intent.ts

import StringEnum from './StringEnum';
export const Intent = StringEnum(['success', 'warning', 'error', 'info']);
export type Intent = keyof typeof Intent;

/**
 * This allows you to declare an enum that can be used a both a type and value, while still allowing the user to use plain strings.
 * The option to use plain strings is good when you are developing a library that might be used in a none TS project.
 * example
````
const Message = (intent:Intent) => (message: string) => {
 ...
}

const SendWarningMessage = (message:string) => {
  Message(Intent.warning)(message);
}


const SendSuccessMessage = (message:string) => {
  Message('success')(message);
}
````
 */

StringEnum.ts

export default function StringEnum<T extends string>(o: T[]): { [K in T]: K } {
  return o.reduce((res, key) => {
    res[key] = key;
    return res;
  }, Object.create(null));
}