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Function: match() ​

Call Signature ​

match<T, E, A>(matcher, result): A

Performs the same basic functionality as unwrapOrElse, but instead of simply unwrapping the value if it is Ok and applying a value to generate the same default type if it is Err, lets you supply functions which may transform the wrapped type if it is Ok or get a default value for Err.

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

Instead of code like this:

ts
import Result, { isOk, match } from 'true-myth/result';

const logValue = (mightBeANumber: Result<number, string>) => {
  console.log(
    mightBeANumber.isOk
      ? mightBeANumber.value.toString()
      : `There was an error: ${unsafelyGetErr(mightBeANumber)}`
  );
};

...we can write code like this:

ts
import Result, { match } from 'true-myth/result';

const logValue = (mightBeANumber: Result<number, string>) => {
  const value = match(
    {
      Ok: n => n.toString(),
      Err: e => `There was an error: ${e}`,
    },
    mightBeANumber
  );
  console.log(value);
};

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.

Type Parameters ​

T ​

T

E ​

E

A ​

A

Parameters ​

matcher ​

Matcher<T, E, A>

A lightweight object defining what to do in the case of each variant.

result ​

Result<T, E>

The result instance to check.

Returns ​

A

Call Signature ​

match<T, E, A>(matcher): (result) => A

Performs the same basic functionality as unwrapOrElse, but instead of simply unwrapping the value if it is Ok and applying a value to generate the same default type if it is Err, lets you supply functions which may transform the wrapped type if it is Ok or get a default value for Err.

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

Instead of code like this:

ts
import Result, { isOk, match } from 'true-myth/result';

const logValue = (mightBeANumber: Result<number, string>) => {
  console.log(
    mightBeANumber.isOk
      ? mightBeANumber.value.toString()
      : `There was an error: ${unsafelyGetErr(mightBeANumber)}`
  );
};

...we can write code like this:

ts
import Result, { match } from 'true-myth/result';

const logValue = (mightBeANumber: Result<number, string>) => {
  const value = match(
    {
      Ok: n => n.toString(),
      Err: e => `There was an error: ${e}`,
    },
    mightBeANumber
  );
  console.log(value);
};

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.

Type Parameters ​

T ​

T

E ​

E

A ​

A

Parameters ​

matcher ​

Matcher<T, E, A>

A lightweight object defining what to do in the case of each variant.

Returns ​

(result): A

Parameters ​

result ​

Result<T, E>

Returns ​

A