unnullish

unnullish returns undefined if value is nullish, otherwise it executes callback and returns the result. It is an opposite function of the nullish coalescing operator (??).

Usage

unnullish

unnullish<T, R>(value: T | null | undefined, callback(v: T) => R): R | undefined

The function is useful when you want to apply some transformation functions to optional values. For example,

import { unnullish } from "https://deno.land/x/unnullish@v1.0.2/mod.ts";

type Options = {
  foo?: string;
  bar?: number;
};

function sayHello(v: string): string {
  return `Hello ${v}`;
}

const options: Options = {
  foo: unnullish(Deno.env.get("foo"), (v) => sayHello(v)),
  // instead of
  //foo: Deno.env.get("foo") != null
  //  ? sayHello(Deno.env.get("foo"))
  //  : undefined,

  bar: unnullish(Deno.env.get("bar"), (v) => parseInt(v, 10)),
  // instead of
  //bar: Deno.env.get("bar") != null
  //  ? parseInt(Deno.env.get("bar"), 10)
  //  : undefined,
};

Note that the function returns undefined even the input is null, mean that you may need to use nullish coalescing operator to normalize the result. For example,

import { unnullish } from "https://deno.land/x/unnullish@v1.0.2/mod.ts";

console.log(unnullish(null, () => 0));
// -> undefined
console.log(unnullish(undefined, () => 0));
// -> undefined

console.log(unnullish(null, () => 0) ?? null);
// -> null
console.log(unnullish(undefined, () => 0) ?? null);
// -> null

License

The code follows MIT license written in LICENSE. Contributors need to agree that any modifications sent in this repository follow the license.