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I'm trying to search for an object inside an array with the following code:

function countUniqueBoxes(array,key)
{
    var output = [];

    var value = false;
    var obj = false;

    for(var i = 0; i < array.length; ++i)
    {
        value = array[i][key];
        obj = {'Box': value};

        if(output[i] === obj)
        {
            continue;
        }
        else
        {
            output.push(obj);
        }
    }
    return output;
}

The array that Is passed to this function, contains multiples objects, with duplicate values. As you can see, I Im trying to sort out the duplicates, and Insert the unique values, but Instead, ALL the values Is added to my output array, even the duplicate values.

If I do like this Instead:

 for(var i = 0; i < array.length; ++i)
    {
        value = array[i][key];
        if(output.indexOf(value) === -1)
        {
            output.push(value);
        }
    }

It works. The unique values are added to my output array. But I want add the values as objects to my array.

What Is wrong?

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1

3 Answers 3

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6

You are using strict comparison operator (===) to compare two completely different objects. This will not work, i.e.

{} === {} // Never true!

If you need to sort out objects that look like duplicates, you will need to use another mechanism, like comparing the objects' properties instead.

I think it boils down to how you would like to define a "duplicate" object in your array. There are two possibilities:

  1. A duplicate object is only duplicate if it is in the array more than one time, but it is still the same object in memory
  2. A duplicate object is only duplicate if some (or all) of the object's properties are identical to another object's properties

Depending on your situation, the solution will vary greatly, but the generic approach would be a loop inside a loop - the main loop will take one object in the array and then loop through that same array once again to see if it is in the array more than once.

There is definitely room for optimisation. Perhaps you could even refactor your code to not allow an object to be inserted to the array if it looks like duplicate in the first place.

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2 Comments

But how can I search for an object inside an array? How do I compare object properties?
See my updated answer - I have added some hints. There are plenty of examples about how to find duplicate objects in array on the internets, so I restricted myself to a human text only.
1

because you directly compare the objects in your code, you can try :

 if(output[i] output[i]['Box'] === obj['Box'])
 {
     continue;
 }

in your code you need to do another for loop in output to do the compare, like:

function isHasObj(output,obj){
  for (var j = 0; j < output.length; ++j) {
      if (output[j]['Box'] === obj['Box']) {
         return true;
      }
  }
  return false;
}

and change the if like:

if (isHasObj(output,obj)) {
    continue;
}
else {
    output.push(obj);
}
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3 Comments

I get output[i] is undefined
@Bryan yes, in your code you need to do another for loop as I updated above.
The if-statement in you answer does not work? I get a: missing ) after condition.
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You can convert the javascript object to json String then compare tow strings.

 JSON.stringify(obj1) === JSON.stringify(obj2) 

 x = {a: 47, b: 2};
 y = {b: 2, a: 47};
if(JSON.stringify(x) === JSON.stringify(y) ){
  //true
}else{
//false
}
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2 Comments

The problem with this is that the order of properties is not guaranteed to be alphabetical when you JSON.stringify() the objects, thus the comparison might not work even for objects that are, in fact, identical in structure.
you can sort the properties of object then check object inequalities .

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