Javascript monad Maybe with Monet

The Monad Maybe

Maybe aka option or optional is very useful for preventing null. Using the Javascript library Monet it's quite easy to use this monad.

Preventing null

You have a variable but don't know if it's null. With Maybe, you wrap it and test if it is "some".

	var couldBeNull = Maybe.fromNull(suspiciousVariable);
	if (couldBeNull.isSome()) {
	// Ok
	} else {
	// KO!
	}

view raw Monet Maybe.js hosted with ❤ by GitHub

Transform or map

Monads are also useful to transform a value to another. Think of this example:

	var text = "10";
	var integer = parseInt(text);
	var array = new Array(integer);
	for (var i=0; i<integer; i++) {
	array[i] = i;
	}
	console.log(array); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

view raw Old.js hosted with ❤ by GitHub

Each step is instancing a variable and making a "halt". With a monad, you can "go with the flow" and do it all in one step:

	console.log(
	Some("10").map(function(text) {
	return parseInt(text);
	}).map(function(integer) {
	return new Array(integer);
	}).map(function(array) {
	for (var i=0; i<array.length; i++) {
	array[i] = i;
	}
	return array;
	}).some();
	); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

view raw Monet Maybe Mapping.js hosted with ❤ by GitHub

Sample

https://jsfiddle.net/yapdd5xv/15/