Filter object array against another object array

Question

I have two arrays simplified like this.

var a = [{
 number: 1,
 name: "A"
}, {
 number: 2,
 name: "B"
}, {
 number: 3,
 name: "C"
}, {
 number: 4,
 name: "D"
}, {
 number: 5,
 name: "E"
}, {
 number: 6,
 name: "F"
}];

var b = [{
 number: 3,
 name: "C"
}, {
 number: 6,
 name: "F"
}];

What I want is to return an array where a is filtered against b. So the result is this.

var result = [{
 number: 1,
 name: "A"
}, {
 number: 2,
 name: "B"
}, {
 number: 4,
 name: "D"
}, {
 number: 5,
 name: "E"
}];

Have looked at alot of other solutions here on stack overflow but can't get it to work.

I am ok with using libaries like underscore.

what does "filtered against" mean? you want to combine them? you want all the items in the vesica pisces? you want unique items? clarify. — I wrestled a bear once.
– I wrestled a bear once., Commented Jan 13, 2017 at 14:57
If you are using lodash(upgraded underscore) you can simply find it using _.differenceBy(). Checkout my answer — Nidhin David
– Nidhin David, Commented Jan 13, 2017 at 15:23

Maxim Kuzmin · Accepted Answer · 2017-01-13 15:08:29Z

6

It is possible to achieve with lodash by the one-line solution.

var a = [{
 number: 1,
 name: "A"
}, {
 number: 2,
 name: "B"
}, {
 number: 3,
 name: "C"
}, {
 number: 4,
 name: "D"
}, {
 number: 5,
 name: "E"
}, {
 number: 6,
 name: "F"
}];

var b = [{
 number: 3,
 name: "C"
}, {
 number: 6,
 name: "F"
}];

var result = _.differenceWith(a, b, _.isEqual);

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

answered Jan 13, 2017 at 15:08

Maxim Kuzmin

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Comments

Nidhin David · Accepted Answer · 2017-01-13 15:24:33Z

2

var a = [{
 number: 1,
 name: "A"
}, {
 number: 2,
 name: "B"
}, {
 number: 3,
 name: "C"
}, {
 number: 4,
 name: "D"
}, {
 number: 5,
 name: "E"
}, {
 number: 6,
 name: "F"
}];

var b = [{
 number: 3,
 name: "C"
}, {
 number: 6,
 name: "F"
}];

var _ = require('lodash');
var result = _.differenceBy(a,b,'name');

For more informaiton please refer Lodash documentation: https://lodash.com/docs/#differenceBy

edited Jan 13, 2017 at 15:24

answered Jan 13, 2017 at 15:18

Nidhin David

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4 Comments

Maxim Kuzmin Over a year ago

what if author wants to check not only name field?

Nidhin David Over a year ago

@MaximKuzmin Your solution is better.

stig Over a year ago

So to use lodash I have to change out all my underscore functions? Doesn't look like they work together.

Nidhin David Over a year ago

@stibay Actually lodash is a clone of underscore with more features(plenty more). It is a good idea to switch to lodash. Most of the functions will be identical, though some may be breaking. Just verify it. Meanwhile you can use(install) each funcitons of lodash individually. Checkout npmjs.com/browse/keyword/lodash-modularized You can install this function alone by npm install lodash.differenceBy

luiscrjr · Accepted Answer · 2017-01-13 16:11:21Z

2

You can use Array#filter. Something like that:

const filterData = (a,b) => {
    return a.filter( (itemA) => {
        return b.some( (itemB) => { 
            return (itemA.number === itemB.number); 
         });
  });
}

I just created a fiddle to test the code: https://jsfiddle.net/mrlew/pb1qqeyd/3/ (you'll have to open console to check results).

Or... in one-line:

const filterData = (a,b) => a.filter( (itemA) => b.some( (itemB) => (itemA.number === itemB.number) ) );

EDIT: thanks to @kzh suggestions, edited to use .some.

edited Jan 13, 2017 at 16:11

answered Jan 13, 2017 at 15:07

luiscrjr

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1 Comment

kzh Over a year ago

You should probably use some instead of forEach so that it does not iterate the entire array.

Abdul Mateen Mohammed · Accepted Answer · 2017-01-13 15:20:42Z

1

You can use the in-built filter function in JavaScript to filter an array with another array check the below code snippet.

var a = [{
  number: 1,
  name: "A"
}, {
  number: 2,
  name: "B"
}, {
  number: 3,
  name: "C"
}, {
  number: 4,
  name: "D"
}, {
  number: 5,
  name: "E"
}, {
  number: 6,
  name: "F"
}];

var b = [{
  number: 3,
  name: "C"
}, {
  number: 6,
  name: "F"
}];

var result = a.filter(function(currentValue, index, arr) {
  var found = false;
  for (var i = 0; i < b.length; i++) {
    if (currentValue.number === b[i].number) {
      found = true;
      break;
    }
  }

  if (!found) {
    return currentValue;
  }
});

console.log(result);

answered Jan 13, 2017 at 15:20

Abdul Mateen Mohammed

1,8841 gold badge13 silver badges21 bronze badges

Comments

Nenad Vracar · Accepted Answer · 2017-01-13 15:09:49Z

0

You can do this with plain javascript using filter(), some() and every().

var a = [{"number":1,"name":"A"},{"number":2,"name":"B"},{"number":3,"name":"C"},{"number":4,"name":"D"},{"number":5,"name":"E"},{"number":6,"name":"F"}]
var b = [{"number":3,"name":"C"},{"number":6,"name":"F"}]

var result = a.filter(function(o) {
  return !b.some(function(e) {
    return Object.keys(o).length == Object.keys(e).length && Object.keys(o).every(function(k) {
      return e[k] == o[k]
    })
  })
})

console.log(result)

answered Jan 13, 2017 at 15:09

Nenad Vracar

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Comments

Bhabani P · Accepted Answer · 2017-01-13 15:18:07Z

0

var v1 = JSON.parse(a);
var v2 = JSON.parse(b);

var v3 = [] ;


function objectEquals(v1, v2) {

    if (typeof(v1) !== typeof(v2)) {
        return false;
    }
if (v1 instanceof Object && v2 instanceof Object) {

  for (k in v1) {
            r = objectEquals(v1[k], v2[k]);
            if (!r) {
              v3.push(v1[k]);  

            }
        }



}

}

// call the above method passing your two object, and return a new unique array


objectEquals(v1, v2) ;

answered Jan 13, 2017 at 15:18

Bhabani P

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