unfold-with
An unfold helper, inspired by this awesome article.
Install:
npm i unfold-withAPI
unfoldWidth((value) => [value, next-value] || null, initial-value)
-
(value) => [value, next-value]. Required. A function which takes a value and returns either an array of the form[value, next-value]ornull || undefined. -
initial-value. Optional. If present, the first call to the function above will be invoked with this value.
Examples
A simple range:
const unfold = require("unfold-with");
const rangePositive = (start, end) =>
unfold((x) => (x <= end ? [x, x + 1] : null), start);
console.log(rangePositive(-2, 2)); // [ -2, -1, 0, 1, 2 ]Or a tree:
const unfold = require("unfold-with");
// example taken from http://raganwald.com/2016/11/30/anamorphisms-in-javascript.html
const tree = {
label: 1,
children: [
{
label: 2,
children: [
{
label: 4,
children: [],
},
{
label: 5,
children: [],
},
],
},
{
label: 3,
children: [
{
label: 6,
children: [],
},
],
},
],
};
const depthFirst = (input) =>
unfold(
(forest) =>
forest.length > 0
? [forest[0].label, forest[0].children.concat(forest.slice(1))]
: null,
input
);
const breadthFirst = (input) =>
unfold(
(forest) =>
forest.length > 0
? [forest[0].label, forest.slice(1).concat(forest[0].children)]
: null,
input
);
console.log(
depthFirst([tree]), // [ 1, 2, 4, 5, 3, 6 ]
breadthFirst([tree]) // [ 1, 2, 3, 4, 5, 6 ]
);