Function find

Safely search for an element in an array.

This function behaves like Array.prototype.find, but returns Maybe<T> instead of T | undefined.

Examples

The basic form is:

import Maybe from 'true-myth/maybe';

let array = [1, 2, 3];
Maybe.find(v => v > 1, array); // Just(2)
Maybe.find(v => v < 1, array); // Nothing
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The function is curried so you can use it in a functional chain. For example (leaving aside error handling on a bad response for simplicity), suppose the url https://arrays.example.com returned a JSON payload with the type Array<{ count: number, name: string }>, and we wanted to get the first of these where count was at least 100. We could write this:

import Maybe from 'true-myth/maybe';

type Item = { count: number; name: string };
type Response = Array<Item>;

// curried variant!
const findAtLeast100 = Maybe.find(({ count }: Item) => count > 100);

fetch('https://arrays.example.com')
  .then(response => response.json() as Response)
  .then(findAtLeast100)
  .then(found => {
    if (found.isJust) {
      console.log(`The matching value is ${found.value.name}!`);
    }
  });
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