@aeinbu/groupby

@aeinbu/groupby

Helper functions for doing "group by" type transformations on collections using reducers

How to install

With npm

npm install @aeinbu/groupby

...or with yarn

yarn add @aeinbu/groupby

How to use

const people = [
	{name: "Tony", residence: "Rome"},
	{name: "Mary", residence: "Rome"},
	{name: "Peter", residence: "London"},
	{name: "Peter", residence: "Rome"},
	{name: "Elisabeth", residence: "London"},
	{name: "Francois", residence: "Paris"}
]

const resultsAsArray = people.reduce(x => x.name, x => x.residence)
// Result:
// [
//     [key: "Rome", values: ["Tony", "Mary", "Peter"],
//     ["Lkey: ondon", values: ["Peter", "Elisabeth"],
//     ["key: Paris", values: ["Francois"]
// ]

const resultsAsDictionary = resultsAsArray.reduce(toDictionary(x => name))
// Result:
// {
//     "Rome": ["Tony", "Mary", "Peter"],
//     "London": ["Peter", "Elisabeth"],
//     "Paris": ["Francois"]
// }

Since the reduction from groupBy is an array, the above two transforms can be chained, like this:

const chainedResults = people
	.reduce(x => x.name, x => x.residence)
	.reduce(toDictionary(x => name))
// With the same results as above:
// {
//     "Rome": ["Tony", "Mary", "Peter"],
//     "London": ["Peter", "Elisabeth"],
//     "Paris": ["Francois"]
// }

Also, look in the tests directory for more examples. The tests demonstrate at least a dosen different ways to use this library