Filtering array of objects with arrays based on nested value

Question

I am trying to filter an array, based on some nested object. I prepared some Fiddle

Input array looks like this:

let arrayOfElements =      [         {            "name": "a",            "subElements":             [              {"surname": 1},              {"surname": 2}            ]         },         {            "name": "b",            "subElements":             [              {"surname": 3},              {"surname": 1}            ]         },         {            "name": "c",            "subElements":             [              {"surname": 2},              {"surname": 5}            ]         }     ]; 

I want the output for this case, to look like this:

let filteredArray =      [         {           "name": "a",           "subElements":            [             {"surname": 1}           ]         },         {           "name": "b",           "subElements":            [             {"surname": 1}           ]         } ]; 

I am using this formula to do that:

let filteredArray = arrayOfElements.filter((element) => element.subElements.some((subElement) => subElement.surname === 1)); 

Output is almost good, but it returns objects with all objects with surnames (better check that fiddle :D), instead of cutting them away. How can i improve the filtering ?

Answer 1

This way you can go as deep as you want in an array and filter elements at any level,

arrayOfElements.map((element) => {   return {...element, subElements: element.subElements.filter((subElement) => subElement.surname === 1)} }) 

Spread operator will expand element and then filtered subElements will override the subElements in element.

Answer 2

After you call filter, you need to pipe the results to map, like this:

let filteredArray = arrayOfElements   .filter((element) =>      element.subElements.some((subElement) => subElement.surname === 1))   .map(element => {     let newElt = Object.assign({}, element); // copies element     return newElt.subElements.filter(subElement => subElement.surname === '1');   }); 

I am assuming here that you don't want to manipulate the original array. So, I am using Object.assign.