Comparing two arrays of objects and exclude the elements who match values into new array in JS

Question

here is my use case in JavaScript   I have two arrays of objects which have properties that match  id  amp  name    var result1          id 1  name  Sandra   type  user   username  sandra         id 2  name  John   type  admin   username  johnny2         id 3  name  Peter   type  user   username  pete         id 4  name  Bobby   type  user   username  be bob       var result2          id 2  name  John   email  johnny example com         id 4  name  Bobby   email  bobby example com       var props     id    name      My goal is to have another array of objects containing only the elements which did not match  Like this   var result          id 1  name  Sandra         id 3  name  Peter        I know that there is a way of doing this by going from result1 compare each object with the objects of result2  then compare their keys  and if did n match  put the values in another object then push it in new array  but I wonder is there any more elegant way  like using lo-dash or underscore or something similar   Thank you

User · Accepted Answer

Just using the Array iteration methods built into JS is fine for this:

_x000D_

var result1 = [_x000D_
    {id:1, name:'Sandra', type:'user', username:'sandra'},_x000D_
    {id:2, name:'John', type:'admin', username:'johnny2'},_x000D_
    {id:3, name:'Peter', type:'user', username:'pete'},_x000D_
    {id:4, name:'Bobby', type:'user', username:'be_bob'}_x000D_
];_x000D_
_x000D_
var result2 = [_x000D_
    {id:2, name:'John', email:'[email protected]'},_x000D_
    {id:4, name:'Bobby', email:'[email protected]'}_x000D_
];_x000D_
_x000D_
var props = ['id', 'name'];_x000D_
_x000D_
var result = result1.filter(function(o1){_x000D_
    // filter out (!) items in result2_x000D_
    return !result2.some(function(o2){_x000D_
        return o1.id === o2.id;          // assumes unique id_x000D_
    });_x000D_
}).map(function(o){_x000D_
    // use reduce to make objects with only the required properties_x000D_
    // and map to apply this to the filtered array as a whole_x000D_
    return props.reduce(function(newo, name){_x000D_
        newo[name] = o[name];_x000D_
        return newo;_x000D_
    }, {});_x000D_
});_x000D_
_x000D_
document.body.innerHTML = '<pre>' + JSON.stringify(result, null, 4) +_x000D_
        '</pre>';

_x000D_

If you are doing this a lot, then by all means look at external libraries to help you out, but it's worth learning the basics first, and the basics will serve you well here.

User · Answer

Here is another solution using Lodash   var     require  lodash     var result1          id 1  name  Sandra   type  user   username  sandra         id 2  name  John   type  admin   username  johnny2         id 3  name  Peter   type  user   username  pete         id 4  name  Bobby   type  user   username  be bob       var result2          id 2  name  John   email  johnny example com         id 4  name  Bobby   email  bobby example com          filter all those that do not match var result   types1 filter function o1          if match found return false     return   findIndex types2    id   o1 id   name   o1 name       -1   false   true       console log result

User · Answer

well  this using lodash or vanilla javascript it depends on the situation   but for just return the array that contains the duplicates it can be achieved by the following  offcourse it was taken from  1983  var result   result1 filter function  o1        return result2 some function  o2            return o1 id     o2 id     return the ones with equal id               if you want to be more clever    let result   result1 filter o1   gt  result2 some o2   gt  o1 id     o2 id

User · Answer

Check out difference and xor in lodash

User · Answer

The same result can be achieved using Lodash    x000D   x000D  var result1     x000D       id 1  name  Sandra   type  user   username  sandra    x000D       id 2  name  John   type  admin   username  johnny2    x000D       id 3  name  Peter   type  user   username  pete    x000D       id 4  name  Bobby   type  user   username  be bob   x000D     x000D   x000D  var result2     x000D       id 2  name  John   email  johnny example com    x000D       id 4  name  Bobby   email  bobby example com   x000D     x000D   x000D  var result3     result1   x000D           differenceBy result2   id    name   x000D           map   partial   pick      id    name    x000D           value    x000D   x000D  console log result3   x000D   lt script src  https   cdn jsdelivr net lodash 4 16 4 lodash min js  gt  lt  script gt  x000D   x000D   x000D    You can get the desired result applying a difference between both arrays using the properties  id  and  name  as a way to  link  elements between them  If any of those properties are different  the elements are considered different  improbably in your case because id seems to be unique    Lastly  you have to map the result in order to  omit  the undesired properties of the object   Hope it helps

User · Answer

I have searched a lot for a solution in which I can compare two array of objects with different attribute names  something like a left outer join   I came up with this solution  Here I used Lodash  I hope this will help you    var Obj1          id 1  name  Sandra         id 2  name  John           var Obj2           id 2  name  John          id 4  name  Bobby       var Obj3   lodash differenceWith Obj1  Obj2  function  o1  o2        return o1  id       o2   id        console log Obj3        id 1  name  Sandra

[javascript] Comparing two arrays of objects, and exclude the elements who match values into new array in JS

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