Filtering array of objects with arrays based on ne

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

function display_message() {
  let arrayOfElements = [{
    "name": "a",
    "subElements": [{
      "surname": 1
    }, {
      "surname": 2
    }]
  }, {
    "name": "b",
    "subElements": [{
      "surname": 3
    }, {
      "surname": 1
    }]
  }, {
    "name": "c",
    "subElements": [{
      "surname": 2
    }, {
      "surname": 5
    }]
  }];
  // console.log(arrayOfElements);
var surname = 1;
  let filteredArray = arrayOfElements.filter((element) => element.subElements.some((subElement) => subElement.surname === surname));

  for(var data in filteredArray){
    filteredArray[data].subElements = {"surname": surname};
    }
  console.log(filteredArray);

}

<input type="button" onclick="display_message();" value="click"/>

Answer 2

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 it will override the subElements key with filtered values.

Answer 3

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

is more correctly

Answer 4

You can make it generic as well:

Logic

• Find all distinct surnames and loop over them
• Filter every object to check if surnames exists. If yes, copy object using Object.assign and set subElements value to filtered list.
• Create a temp array to hold all similar objects and push copied object to it.
• Push this array to final array on every iteration of distinct surname.

Sample

let arrayOfElements=[{name:"a",subElements:[{surname:1},{surname:2}]},{name:"b",subElements:[{surname:3},{surname:1}]},{name:"c",subElements:[{surname:2},{surname:5}]}];
 let distinct_surnames = [];
 arrayOfElements.forEach(function(el) {
   el.subElements.forEach(function(s) {
     if (distinct_surnames.indexOf(s.surname) < 0) distinct_surnames.push(s.surname)
   });
 })

 let result = [];
 distinct_surnames.forEach(function(sn) {
   let inter = [];
   arrayOfElements.forEach(function(el) {
     let f = el.subElements.filter(function(sub) {
       return sub.surname === sn;
     });
     if (f.length > 0) {
       let _tmp = Object.assign({}, el);
       _tmp.subElements = f;
       inter.push(_tmp);
     }
   });
   result.push(inter);
 })
 console.log(result)

Note: Arrow functions are used to keep the reference of this. If you are not using this inside function, you can use normal functions as well.

Answer 5

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.

Answer 6

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

  });