Question

121

Reverse-Mapping for String Enums

rated 0 times [ 123] [ 2] / answers: 1 / hits: 44584 / 7 Years ago, mon, july 3, 2017, 12:00:00

I wanted to use string enums in typescript but I can't see a support for reversed mapping in it.
I have an enum like this:

enum Mode {

    Silent = Silent,

    Normal = Normal,

    Deleted = Deleted

}

and I need to use it like this:

let modeStr: string;

let mode: Mode = Mode[modeStr];

and yes I don't know what is it there in modeStr string and I need it parsed to the enum or a fail at parsing in runtime if the string is not presented in the enum definition.
How can I do that as neat as it can be?
thanks in advance

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

victorr

Add To Favorites

Follow

Total Points: 193

Total Questions: 86

Total Answers: 105

Location: Pitcairn Islands

Member since Thu, Jun 24, 2021

3 Years ago

victorr questions

1 Dot product of two arrays in Javascript

Fri, Nov 13, 20, 00:00, 4 Years ago

1 Rendering a component only after API request is finished React hooks

Thu, Oct 15, 20, 00:00, 4 Years ago

1 Thousand separator input with React Hooks

Sat, Jul 25, 20, 00:00, 4 Years ago

1 Typescript object destructuring is caught by ESLint no-unused-vars rule

Fri, Jul 10, 20, 00:00, 4 Years ago

1 How to pass data to {props.children}

Thu, Jun 11, 20, 00:00, 4 Years ago

View All

answered 7 Years ago elians · Accepted Answer

We can make the Mode to be a type and a value at the same type.

type Mode = string;

let Mode = {

    Silent: Silent,

    Normal: Normal,

    Deleted: Deleted

}



let modeStr: string = Silent;

let mode: Mode;



mode = Mode[modeStr]; // Silent

mode = Mode.Normal; // Normal

mode = Deleted; // Deleted

mode = Mode[unknown]; // undefined

mode = invalid; // invalid

A more strict version:

type Mode = Silent | Normal | Deleted;

const Mode = {

    get Silent(): Mode { return Silent; },

    get Normal(): Mode { return Normal; },

    get Deleted(): Mode { return Deleted; }

}



let modeStr: string = Silent;

let mode: Mode;



mode = Mode[modeStr]; // Silent

mode = Mode.Normal; // Normal

mode = Deleted; // Deleted

mode = Mode[unknown]; // undefined

//mode = invalid; // Error

String Enum as this answer:

enum Mode {

    Silent = <any>Silent,

    Normal = <any>Normal,

    Deleted = <any>Deleted

}



let modeStr: string = Silent;

let mode: Mode;



mode = Mode[modeStr]; // Silent

mode = Mode.Normal; // Normal

//mode = Deleted; // Error

mode = Mode[unknown]; // undefined