Remove element from array inside array of objects if present in another array of objects

Question

I am working with a large array of objects. I have simplified my data structure to the following. Each object has an id and each id has two arrays associated with it type1 and type2.

const arr = [{id: "12345", type1: ["Hat 1", "Hat 3"], type2: ["Hat 2", "Glove 4"]}, 
             {id: "12345", type1: ["Glove 1", "Hat 1"], type2: ["Glove 3", "Hat 2"]},           
             {id: "54321", type1: ["Jacket 1", "Hat 4"], type2: ["Hat 3", "Hat 4"]},
             {id: "54321", type1: ["Glove 2", "Hat 2"], type2: ["Glove 3", "Jacket 4"]},
             {id: "13579", type1: ["Hat 1", "Hat 2"], type2: ["Hat 3", "Hat 4"]},
             {id: "13579", type1: ["Glove 1", "Glove 2"], type2: ["Glove 3", "Glove 4"]}]

I have a "lookup" array of objects. Each object has an id and a title

const lookup = [{id: "12345", title: "Hat 1"},
                {id: "12345", title: "Hat 2"},
                {id: "12345", title: "Glove 3"},
                {id: "54321", title: "Hat 3"} 
                {id: "54321", title: "Jacket 4"},
                {id: "54321", title: "Glove 5"},
                {id: "13579", title: "Hat 2"},
                {id: "13579", title: "Jacket 3"}]

I need to use the "lookup" object for any matching id that has a title I need to remove it from type1 or type2 or both. So my resulting array of objects would look something like so

const result = [{id: "12345", type1: ["Hat 3"], type2: ["Glove 4"]}, 
                {id: "12345", type1: ["Glove 1"], type2: []},           
                {id: "54321", type1: ["Jacket 1", "Hat 4"], type2: ["Hat 4"]},
                {id: "54321", type1: ["Glove 2", "Hat 2"], type2: ["Glove 3"]},
                {id: "13579", type1: ["Hat 1"], type2: ["Hat 3", "Hat 4"]},
                {id: "13579", type1: ["Glove 1", "Glove 2"], type2: ["Glove 3", "Glove 4"]}]

The duplicates and having to search through both arrays for any matching id's is confusing me. Is there a simple way to do this or maybe a better way to structure the data so it's not so convoluted?

Have you made any attempt at all to come up with such a result yourself yet? Please post the code you've tried — CertainPerformance
– CertainPerformance, Commented Aug 23, 2018 at 1:54
should the lookup happen 1:1 i.e. lookup first obj of arr with first obj of lookup? The result array looks a bit confusing. Lookup key 12345 contains titles hat 1, hat 2 and glove 3. In that case the second object(id=12345) in result object should not contain hat 1 in type1 and hat 2 in type 2. — SubSul
– SubSul, Commented Aug 23, 2018 at 3:18
@SubSul That was my mistake. Oversight on my part when i was simplifying the data structure — ees3
– ees3, Commented Aug 23, 2018 at 3:38
Depending on how much control you have over the structure of the lookup data, it would simplify things to structure the "lookup" data as json with key "id" and value as array of all titles for that id like {"12345": ["Hat 1", "Hat 2", "Glove 3"]}. Then you could just loop through the "arr" data, access the lookup key that corresponds to the id and remove any matching types. — benvc
– benvc, Commented Aug 23, 2018 at 4:27

SubSul · Accepted Answer · 2018-08-23 05:20:47Z

1

Loop through arr and for each entry of arr, loop through lookup to compare and modify arr

  for(let arrEntry of arr) {
    let id = arrEntry.id;
    let type1 = arrEntry.type1;
    let type2 = arrEntry.type2;

    for(let lookupEntry of lookup) {
      let title = lookupEntry.title;
      if(lookupEntry.id === id && type1.includes(title)) {
        type1.splice(type1.indexOf(title), 1);
      }
      if(lookupEntry.id === id && type2.includes(title)) {
        type2.splice(type2.indexOf(title), 1);
      }
    }
  }

  console.log(arr)

edited Aug 23, 2018 at 5:20

answered Aug 23, 2018 at 3:43

SubSul

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Comments

Koushik Chatterjee · Accepted Answer · 2018-08-23 13:12:55Z

Let's not mutate the original data, and create a new resultant array. you can use map, filter and some of Array

arr.map(({id, type1, type2}) => ({
    id,
    type1: type1.filter(t => !lookup.some(l => id===l.id && l.title === t)),
    type2: type2.filter(t => !lookup.some(l => id===l.id && l.title === t))
}));

Here is an working example:

const arr =[
     {id: "12345", type1: ["Hat 1", "Hat 3"], type2: ["Hat 2", "Glove 4"]}, 
     {id: "12345", type1: ["Glove 1", "Hat 1"], type2: ["Glove 3", "Hat 2"]},           
     {id: "54321", type1: ["Jacket 1", "Hat 4"], type2: ["Hat 3", "Hat 4"]},
     {id: "54321", type1: ["Glove 2", "Hat 2"], type2: ["Glove 3", "Jacket 4"]},
     {id: "13579", type1: ["Hat 1", "Hat 2"], type2: ["Hat 3", "Hat 4"]},
     {id: "13579", type1: ["Glove 1", "Glove 2"], type2: ["Glove 3", "Glove 4"]}
  ],
  lookup = [
     {id: "12345", title: "Hat 1"},
     {id: "12345", title: "Hat 2"},
     {id: "12345", title: "Glove 3"},
     {id: "54321", title: "Hat 3"}, 
     {id: "54321", title: "Jacket 4"},
     {id: "54321", title: "Glove 5"},
     {id: "13579", title: "Hat 2"},
     {id: "13579", title: "Jacket 3"}
  ],
  res = arr.map(({id, type1, type2}) => ({
	  id,
	  type1: type1.filter(t => !lookup.some(l => id===l.id && l.title === t)),
	  type2: type2.filter(t => !lookup.some(l => id===l.id && l.title === t))
  }));
  
  console.log(res);

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