lodash - How can i get arrays intersection include duplicate values using Javascript - Stack Overflow

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I need something like lodash.intersectionWith but I also need duplicated values in result array.

Example:

var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];
var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];
_.intersectionWith(objects, others, _.isEqual);

Expected Result:

[{ 'x': 1, 'y': 2 },{ 'x': 1, 'y': 2 }]

Thanks in advance!

I need something like lodash.intersectionWith but I also need duplicated values in result array.

Example:

var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];
var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];
_.intersectionWith(objects, others, _.isEqual);

Expected Result:

[{ 'x': 1, 'y': 2 },{ 'x': 1, 'y': 2 }]

Thanks in advance!

• javascript
• lodash

Share Improve this question Follow edited May 25, 2016 at 10:51 Emna Ayadi 2,46088 gold badges3939 silver badges7979 bronze badges asked May 25, 2016 at 10:16 MikhailMikhail 1,02822 gold badges1414 silver badges3030 bronze badges 2

• It's not exactly clear why you expect there to be 2 copies of that object and not 3. – Omri Aharon Commented May 25, 2016 at 10:22
• Because array #1 has 2 values matching array #2 I'd guess – Randy Commented May 25, 2016 at 10:23

Add a ment  | 

3 Answers 3

Sorted by: Reset to default 3

You can find the intersection by filtering out items from the first array that don't match items in the second. Any duplicates in the first array will be kept.

var intersectwith = function(f,xs,ys){
    return xs.filter(function(x){
        return ys.some(function(y){
            return f(x,y);
        });
    });
};

var equals = function(x,y){
    return x === y;
};
console.log(intersectwith(equals, [1,2,3], [1,1,2,2,4]));
console.log(intersectwith(equals, [1,1,2,2,4], [1,2,3]));

Or, more readably, using ES6:

const intersectwith = (f,xs,ys) => xs.filter(x => ys.some(y => f(x,y)));
const equals = (x,y) => x === y;

console.log(intersectwith(equals, [1,2,3], [1,1,2,2,4]));
console.log(intersectwith(equals, [1,1,2,2,4], [1,2,3]));

Substitute _.isEqual for equals for paring objects: jsfiddle.

Useful documentation:
Array.prototype.filter
Array.prototype.some

You can make use of differenceWith() to get the difference between the source object and the symmetric difference of the source object and the others object using xorWith().

var result = _.differenceWith(
  objects, 
  _.xorWith(objects, others, _.isEqual), 
  _.isEqual
);

var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];
var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];


var intersection = _.intersectionWith(objects, others, _.isEqual);

var result = _.differenceWith(
  objects, 
  _.xorWith(objects, others, _.isEqual), 
  _.isEqual
);

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

<script src="https://cdnjs.cloudflare./ajax/libs/lodash.js/4.13.1/lodash.js"></script>

Use reduce to validate each object in the first array, then check if that object exists in the second array. If it exists, reduce will push that object into its array.

The reduce function will return that new array automagically.

var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 2 }];
var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];

var res = objects.reduce(
  function(arr, obj){
    if(containsObject(obj, others))
      arr.push(obj);
    return arr;
  }, 
  []
);


function containsObject(obj, list) {
    var x;
    var ret = false;
  
    list.forEach(function(s){
      ret = JSON.stringify(s) == JSON.stringify(obj);
    });

    return ret;
}

console.log(res);

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