Sort/intersect two arrays into two new ones.

Question

let's assume I have two lists. One existing with some names and a new one with maybe some new names, deleted names or still the same names.

var currentList = ['Daniel', 'Lara', 'Horst'];
var newList = ['Mario', 'Lara'];

// Expected result
toDelete = ['Daniel', 'Horst']; 
toAdd = ['Mario'];

At the end I need two arrays which contains the new names and those which can be deleted. The names which appear in both array can be ignored.

I don't really know what to call this type of "sorting", so even a buzzword could help. Notice I don't have jQuery at all.

Thanks in advance.

If you don't have limitation on third party libraries, take a look at http://underscorejs.org/. It's a must-know for these kind of things. In particular _.intersection(), _.difference() — SDekov, Jul 07 '15 at 14:54
Change your initial data types to objects, which store internally as hashtables. This can improve your performance from O(n^2) to O(n). — bcorso, Jul 07 '15 at 15:17

Jamiec · Accepted Answer · 2015-07-07T15:01:14.650

2

Thats pretty straightforward, you could do it with 2 loops:

var currentList = ['Daniel', 'Lara', 'Horst'];
var newList = ['Mario', 'Lara'];

var toDelete = [];
var toAdd = [];
for(var i=0;i<newList.length;i++){
    if(currentList.indexOf(newList[i]) >-1)
        toAdd.push(newList[i])
}

for(var i=0;i<currentList.length;i++){
   if(newList.indexOf(currentList[i]) == -1)
       toDelete.push(currentList[i]);
}

console.log('dele',toDelete);
console.log('add',toAdd);

Live example: http://jsfiddle.net/r6L7LpeL/

edited Jul 07 '15 at 15:01

answered Jul 07 '15 at 14:54

Jamiec

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Ah! Thanks that works great, but I already solved it using filter http://jsfiddle.net/r6L7LpeL/1/ – YeppThat'sMe Jul 07 '15 at 15:02

score -1 · Answer 2 · answered Jul 07 '15 at 14:56

First create a third array which is intersection of the current and new list. Second, remove this array from each of the arrays.

Pseudo code:

var intersection_list = intersection(currentList, newList)
var toDelete = currentList - intersectionList;
var toAdd = newList - intersectionList;

You can use the mentioned above library for _.intersection() and _.difference()

Sort/intersect two arrays into two new ones.

2 Answers2