Helper function for exhaustive checks of discriminated unions in TypeScript
npm install assert-neverHelper function for [exhaustive checks][exhaustive-checks] of discriminated
unions in TypeScript.
``
npm install --save assert-never
`ts
import {assertNever} from "assert-never";
type A = {type: 'a'};
type B = {type: 'b'};
type Union = A | B;
function doSomething(arg: Union) {
if (arg.type === 'a') {
return something;
}
if (arg.type === 'b') {
return somethingElse;
}
// TS will error if there are other types in the union
// Will throw an Error when called at runtime. Use assertNever(arg, true)
// instead to fail silently.
return assertNever(arg);
}
[npm-image]: https://badge.fury.io/js/assert-never.svg
[npm-url]: https://badge.fury.io/js/assert-never
[exhaustive-checks]: https://basarat.gitbook.io/typescript/type-system/discriminated-unions#exhaustive-checks