Function match

Performs the same basic functionality as unwrapOrElse, but instead of simply unwrapping the value if it is Just and applying a value to generate the same default type if it is Nothing, lets you supply functions which may transform the wrapped type if it is Just or get a default value for Nothing.

This is kind of like a poor man's version of pattern matching, which JavaScript currently lacks.

Instead of code like this:

import Maybe from 'true-myth/maybe';

const logValue = (mightBeANumber: Maybe<number>) => {
  const valueToLog = Maybe.mightBeANumber.isJust
    ? mightBeANumber.value.toString()
    : 'Nothing to log.';

  console.log(valueToLog);
};
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...we can write code like this:

import { match } from 'true-myth/maybe';

const logValue = (mightBeANumber: Maybe<number>) => {
  const value = match(
    {
      Just: n => n.toString(),
      Nothing: () => 'Nothing to log.',
    },
    mightBeANumber
  );

  console.log(value);
};
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This is slightly longer to write, but clearer: the more complex the resulting expression, the hairer it is to understand the ternary. Thus, this is especially convenient for times when there is a complex result, e.g. when rendering part of a React component inline in JSX/TSX.