lukyanoff / maybe-monad

A Typescript implementation of the Maybe monad

maybe-monad

A Typescript implementation of the Maybe mondad.

Installation

npm install --save maybe-monad

Usage

The Usual use case of the Maybe monday is to make it easier to deal with possibly null or undefined values. A Maybe may have a value or it may not have a value. further processing can take place based on this.

For example:

var someObjectFromAService;

const name: string = Maybe.nullToMaybe(someObjectFromAService)
    .map(object => object.name)
    .filter(name => name != '')
    .do(name => console.log('The name is ' + name))
    .elseDo(() => console.log(`There was no name defined`))
    .defaultTo(`Default Name`);

This is a simple example. If at any point the value is null then no more processing will occur (until we get to defaultTo).

You can use Maybe to deal with logic that does involve null. Use the relevant allowNull operators such as mapAllowNull.

Maybes can be very powerful when combined together using the and, or and combine operators.

Tests

Tests can be run as follows:

git clone https://github.com/Roaders/maybe-monad.git
cd maybe-monad
npm install
npm test

Example

An example can be run as follows:

git clone https://github.com/Roaders/maybe-monad.git
cd maybe-monad
npm install
npm start