TypeScript

A place to talk about TypeScript.

https://www.typescriptlang.org/

320 members

Channels

# General

Team

Mark van den Brink

@markvandenbrink

[Solved] Is there a way to create type from an array?

January 26, 2019 at 3:24pm

Sung Kim

@dance2die

[Solved] Is there a way to create type from an array?

January 26, 2019 at 3:24pm (Edited 3 months ago)

I have a file domElements.ts , which contains a list of DOM element names.

export default [
  "a",
  "abbr",
  ...
  "button",
  ...
];

TypeScript documentation, String Literal Types(https://www.typescriptlang.org/docs/handbook/advanced-types.html#string-literal-types) lets one to specify allowable values.

type Easing = "ease-in" | "ease-out" | "ease-in-out";

Is there a way to create such a type using values from an array imported from domElement.ts?

Here is my attempt to create a type

import domElements from "../domElements";
export type DOMType = domElements;
// export type Target = string | ComponentType<any>;
export type Target = DOMType | ComponentType<any>;

Error message

January 26, 2019 at 4:01pm

Sung Kim@dance2die

4:01pm

Also tried following but domElement could not be found even though it can be used in code above without complaints 🤔

January 26, 2019 at 10:49pm

Sung Kim@dance2die

10:49pm

🤔 Able to pass domElements but printDOMType accepts xxx which is not in domElements array...

1:28am

Hard-coding a list of domElements by hand seems to work (https://codesandbox.io/s/30y547yl91) but...

Edited

1:31am

Passing the array as a variable, domElements infers the typeof arr[number] as string (https://codesandbox.io/s/qrrq24k7q) 🤔

Edited

6:30am

I guess it's not so easy to do so yet... https://stackoverflow.com/a/54061487/4035

6:31am

Took long enough to realize that 😛

6:31am

Maybe I should just copy & paste the list of array values for now in the interface declaration

Edited

January 30, 2019 at 4:59pm

Sung Kim@dance2die

4:59pm

I've finally got it working with a dictionary.

5:00pm

domMap.ts

export default {
  a: "a",
  abbr: "abbr",
  address: "address",
  area: "area",
  ...
}

Edited

5:01pm

Type declaration

5:01pm

import domMap from "./domMap";
type DOMType = keyof typeof domMap;

5:02pm

DOMType now accepts only DOM elements

5:03pm

Demo Sandbox https://codesandbox.io/s/ox79pqpqn9

Edited

5:04pm

Perhaps I should make domMap values as empty string to decrease bundle size 🤔

February 2, 2019 at 7:13pm

Sung Kim@dance2die

7:13pm

To share with the world :) https://www.slightedgecoder.com/2019/02/02/dynamically-build-typescript-string-literal-type/