one-to-many-array-zip

A custom array-combining/zipping function.

Given two sorted arrays whose elements have a one-to-many relationship, and a function that returns true when given two matching elements, efficiently return a new array with the matching elements combined.

const parents = [
	{ name: 'cool dad', coolness: 3 },
	{ name: 'cool cat', coolness: 7 }
]

const children = [
	{ name: 'bobby', coolness: 1 },
	{ name: 'billy', coolness: 3 },
	{ name: 'bubba', coolness: 5 },
	{ name: 'benji', coolness: 6 }
]

const output = oneToManyZip(parents, children, (parent, child) => parent.coolness >= child.coolness)

const expectedOutput =  [
	{
		one: { name: 'cool dad', coolness: 3 },
		many: [
			{ name: 'bobby', coolness: 1 },
			{ name: 'billy', coolness: 3 }
		]
	}, {
		one: { name: 'cool cat', coolness: 7 },
		many: [
			{ name: 'bubba', coolness: 5 },
			{ name: 'benji', coolness: 6 }
		]
	}
]

output // => expectedOutput

oneToManyZip(parentArray, childrenArray, compareFn)

Returns a new array with parentArray.length elements.

Iterates over all the elements in parentArray, and calls compareFn(parentArray[i], childrenArray[j]).

compareFn should return true if the child element belongs to the parent element.

The returned array will have an object for each element in parentArray. The object will have two properties:

• one: the element from parentArray
• many: an array of matching elements from childrenArray

Throws an error if there are any childrenArray elements left after iterating over all the elements in parentArray.

Don't forget, both arrays must be sorted before passing them in!

License

WTFPL