diff --git a/snippets/toHash.md b/snippets/toHash.md new file mode 100644 index 000000000..1e176b15d --- /dev/null +++ b/snippets/toHash.md @@ -0,0 +1,28 @@ +### toHash + +Reduces a given Array-like into a value hash (keyed data store). + +Given an Iterable or Array-like structure, call `Array.prototype.reduce.call()` on the provided object to step over it and return an Object, keyed by the reference value. + +```js +const toHash = ( object, key ) => + Array.prototype.reduce.call( object, ( acc, data, index ) => ( ( acc[ !key ? index : data[ key ] ] = data ), acc ), {} ) +``` + +```js +toHash([ 4,3,2,1 ]); // { 0: 4, 1: 3, 2: 2, 1: 1 } +toHash([ { a: 'label' } ], 'a'); // { label: { a: 'label' } } +// A more in depth example: +let users = [ { id: 1, first: 'Jon' }, { id: 2, first: 'Joe' }, { id: 3, first: 'Moe' } ]; +let managers = [ { manager: 1, employees: [ 2, 3 ] } ]; +// We use function here because we want a bindable reference, but a closure referencing the hash would work, too. +managers.forEach( manager => + manager.employees = manager.employees.map( + function( id ){ + return this[id]; + }, + toHash( users, 'id' ) + ) +); +managers; // [ { manager:1, employees: [ { id: 2, first: "Joe" }, { id: 3, first: "Moe" } ] } ] +```