/asserts

An npm typescript package with useful assert functions

Primary LanguageTypeScriptMIT LicenseMIT

TypeScript asserts

⚠️ this repo is deprecated, please see this one

An npm package with useful assert functions.

Functions

  • assert

    import { assert } from "asserts";

    Assert that a condition is true

    assert(user.id === 123);

  • assertDefined

    import { assertDefined } from "asserts";

    Assert that a value is not null or undefined

    const user: User | null = await fetchUser(endpoint);

assertDefined(user);

// now we are sure that `user` is of User type
const userId = user.id;

  • assertNever

    import { assertNever } from "asserts";

    Ensure that all union variants are checked

    type UnionA = {
  message: "unionA";
};

type UnionB = {
  message: "unionB";
};

type UnionC = UnionA | UnionB;

const aStrangeConstant: UnionC = aStrangeFunction();

switch (aStrangeConstant.message) {
  case "unionA": {
    console.log("I found UnionA");
    break;
  }

  case "unionB": {
    console.log("I found UnionB");
    break;
  }

  default: {
    assertNever(aStrangeConstant);
  }
}

Errors

All functions inside this package raise an AssertFail object once an assertion fails.