At my current job we work a lot with collections, and one of the operations we run is pulling certain items from the collection based on some combination of a key,value. This was happening so much throughout the code that I’ve decided to write my own util function to return a new collection which included only the items I am interested in.
Function
/**
* Given a property and value find all matches in an array of objects
* @param {Array} arr collection to be searched
* @param {String} prop name of property we are searching for
* @param {*} value the value of the specified property we are searching for
* @returns {Array} array with elements that match value for the given property
*/
const searchInArray = (arr, prop, value) => arr.filter(element => element[prop] === value);
Explanation
The searchInArray method takes three arguments: (arr, prop, value). It uses Array.filter to test each element in the collection and returns the matched elements.
The callback to Array.filter looks at the value of the given prop and tests it againt the value we are looking for. The element that pass the test are returned as a new array.
Use
Suppose we have a list of ids (e.g. selected) that we are looking for in a collection (e.g. labels), and we want to return only those elements that match the given ids.
// dummy collection
const labels = [
{ id: 1, name:"string 1", value:"this", other: "that" },
{ id: 2, name:"string 2", value:"this", other: "that" },
{ id: 3, name:"string 2", value:"this", other: "that" },
];
// list of ids we want
const selected = [1,3];
We can use the Array.flatMap method on the selected list, and use our searchInArray method as the callback to Array.flatMap, creating a new list of elements of which we are looking for.
const result = selected.flatMap(id => searchInArray(labels, 'id', id));
// [{ id: 1, name:"string 1", value:"this", other: "that" }, { id: 3, name:"string 2", value:"this", other: "that" }]