TS 2 arrays, if item from first array exists in second array then append to start of second array

Question

I have 2 lists of objects.

One is the list of 'all' objects, the second is the list of 'special' objects.

The first list contains all objects, including special objects.

How do I sort my list of 'all' objects, to order the objects in the following fashion: First 'special' objects, and then all the rest of the objects?

Each object has an id.

For example,

List 1:

[
  {Id: 1, Name: "a", Surname: "a"},
  {Id: 2, Name:"b", Surname:"b"},
  {Id: 3, Name: "c", Surname: "c"}
]

List 2:

[
  {Id: 2, Name:"b", Surname:"b"}
]

How do I order it, so the final list is:

[
  {Id: 2, Name:"b", Surname:"b"},
  {Id: 1, Name: "a", Surname: "a"},
  {Id: 3, Name: "c", Surname: "c"}
]

Majed Badawi · Accepted Answer · 2020-07-06 22:38:06Z

3

You can use the find function to check if one of the two compared elements are special and return the result accordingly in a custom sort function:

let all = [{Id: 1, Name: "a", Surname: "a"}, {Id: 2, Name:"b", Surname:"b"}, {Id: 3, Name: "c", Surname: "c"}];

let special = [{Id: 2, Name:"b", Surname:"b"}];

function sortFunc(a, b) {
  var s1 = special.find(s=>s.Id==a.Id);
  var s2 = special.find(s=>s.Id==b.Id);
  if(s1 && s2) return 0;
  else if(s1) return -1;
  else if(s2) return 1;
  return 0;
}

let sorted = all.slice().sort(sortFunc);

console.log(sorted);

edited Jul 6, 2020 at 22:38

answered Jul 6, 2020 at 22:29

Majed Badawi

28.5k4 gold badges30 silver badges56 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Danila Over a year ago

I would also add that .sort() method is implemented in a mutable way and will change original array. So you probably would like to use .slice() before hand like that let sorted = all.slice().sort(sortFunc);

Frank · Accepted Answer · 2020-07-06 22:38:40Z

0

If you are willing to include lodash you can get the result with this

const List1 = [
  {Id: 1, Name: "a", Surname: "a"}, 
  {Id: 2, Name:"b", Surname:"b"}, 
  {Id: 3, Name: "c", Surname: "c"}
]
const List2 = [
  {Id: 2, Name:"b", Surname:"b"}
]

const SpecialIds = _.map(List2, (v) => { return v.Id })

const List3 = _.sortBy(_.map(List1, (v) => { 
  return _.merge({}, v, { 
    ...v, 
    Type: _.indexOf(SpecialIds, v.Id) === -1 ? '1_Normal' : '0_Special' 
  })
}), ['Type', 'Id'])   


console.log(List3)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.min.js"></script>

answered Jul 6, 2020 at 22:38

Frank

2,2182 gold badges19 silver badges25 bronze badges

Collectives™ on Stack Overflow

TS 2 arrays, if item from first array exists in second array then append to start of second array

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related