Comparing two javascript object algorithm

Question

Super simple example,

var beforeList = [{"name": "A"},{"name": "B"},{"name": "C"}]

var updateList = [{"name": "A"},{"name": "B"},{"name": "D"}]

I have to compare this two and if there is a missing data, i have to insert updatelist data to before List.

So the result I want is,

function someLogicHere(beforeList, updateList){
// some logic here
  return afterList(i.e [{"name": "A"},{"name": "B"},{"name": "C"},{"name": "D"}]  in here) 
}

Any good or awesome lib or plug-in is OK.

I made by myself with forEach but it really is bad.

There isn't a magic function that will do this for you, any solution you find will use a looping mechanism of some kind. Post your code and at least then we can help you improve it to something you would be satisfied with — Kevin B
– Kevin B, Commented Jul 28, 2014 at 14:31
I don't know how to mark as duplicate, but this post: stackoverflow.com/questions/13319150/… goes over the same thing. Oh, and for the record, the library you want is underscore. (underscorejs.org). It's pretty magical. — bearoplane
– bearoplane, Commented Jul 28, 2014 at 14:35
If those objects ONLY contain the 'name' property, then you can just use underscore's pluck() to get the values (like: _(beforeList).pluck('name'); ) and then do a normal union() which will combine two lists, discarding duplicates — bearoplane
– bearoplane, Commented Jul 28, 2014 at 14:38

Praind · Accepted Answer · 2014-07-29 11:48:34Z

1

This should work.

var afterList = beforeList.slice(0); //Clones the array
var elementPresent;

for (var i = 0; i < updateList.length; i++) {
    elementPresent = false;

    for (var j = 0; j < updateList.length; j++) {
        if (updateList[i].name == afterList[j].name){
            elementPresent = true;
            break;
        }
    }

    if(!elementPresent){
        afterList.push({
            "name": updateList[i].name
        });
    }
}

edited Jul 29, 2014 at 11:48

answered Jul 28, 2014 at 14:37

Praind

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3 Comments

mitomed Over a year ago

Are you sure this is working @Johny? What am I missing? jsfiddle.net/4JUqT

Praind Over a year ago

I updated the solution. Didn't realize at first that these things are objects inside array positions.

mitomed Over a year ago

Yeah, thanks what makes me think why the OP set is as valid response without saying anything

Alex K. · Accepted Answer · 2014-07-28 14:38:28Z

0

One way:

var afterList = beforeList.slice(0);

// store all values for easy lookup
var lookup = {};
for (var i in beforeList)
    lookup[beforeList[i].name] = true;

// look for values not in updateList & add to beforeList
for (var i in updateList)
{
   if (!lookup[updateList[i].name])
      afterList.push(updateList[i]);      
}

answered Jul 28, 2014 at 14:38

Alex K.

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