Best way to find index of exact same object in object Array (key is dynamic)

Question

Let's say I have dynamically loaded object each time with different properties and an array of objects of that type:

var obj = {name: someValue, key: someValue2};
var objArray = [{name: someValue, key: someValue2},{name: someValue, key: someValue3}];

I want to find index of objArray which contains the obj. Some elements of objArray can have the same name property but different key property so searching through obj.name is not an option. So far I came up with this solution:

var keys = [];

_.forEach(Object.keys(obj), function(key) {
  keys.push(key, obj[key])
});

var index = _.findIndex(objArray, keys);

This works fine and all but I am looking for something with better performance because this objArray can be very large.

So the question is: Is there a better way to find index of exact same object in object Array?

Update: I forgot to mention that the names of the keys are not specified and can vary each time.

@GirdhariAgrawal — indexOf(object) is not going to work... Use Array#findIndex — Rayon
– Rayon, Commented Aug 29, 2016 at 11:19

GibboK · Accepted Answer · 2016-08-29 17:47:54Z

2

Use Array.prototype.findIndex(), this works only if you know in advance the property you want to check and hard code the rules in the callback for .findIndex().

An example:

var obj = {
  name: 'someValue',
  key: 'someValue3'
};
var objArray = [{
  name: 'someValue',
  key: 'someValue2'
}, {
  name: 'someValue',
  key: 'someValue3'
}];
var index = objArray.findIndex(function(item, index) {
  return (item.name === obj.name) && (item.key === obj.key) ? true : false;
});
console.log('index is: ' + index);

This below it is another approach, basically it takes a JavaScript value (your initial object) and convert to a JSON string, and it uses that string to search within your array. The script works without any recursions, with any number of nested properties for your objects. The order of your property is important in this script, as the conversion to string take it in consideration.

Regarding "best way" is difficult to answer, depending what are your parameters for best way. If you consider performance, you should consider benchmarking your scripts and do test with some real data.

var obj = {
  name: 'someValue',
  key: 'someValue2'
},
objArray = [{
  name: 'someValue',
  key: 'someValue2'
}, {
  name: 'someValue',
  key: 'someValue3'
}];

var str = JSON.stringify(obj),
    index = objArray.findIndex(function(item, index) {
  return str === JSON.stringify(item) ;
});
console.log('index is: ' + index);

edited Aug 29, 2016 at 17:47

answered Aug 29, 2016 at 11:27

GibboK

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5 Comments

Konrad Kahl Over a year ago

This doesn't solve my problem because object can have different keys names: not just 'name' and 'key'

GibboK Over a year ago

@KonradKahl thanks for commenting. I have added an edit to my answer.

GibboK Over a year ago

@KonradKahl it is the order of properties important?

Konrad Kahl Over a year ago

No. Order is not important.

GibboK Over a year ago

@KonradKahl I made an edit, looks if it meet your requirement. Regarding speed and performance only testing and bench-marking can give you a clear idea what is the faster approach.

CodeSmith · Accepted Answer · 2016-08-30 15:37:16Z

I can think of 2 approaches for doing this:

1.) What would speed up the process (especially if you got large array and large objects) is to create some kind of unique key for every object and map it to let's say property called: hash. If you wanna keep it vanilla, the best way to do that might be using the String.hashCode() method.

Iterate trough object OWN (check hasOwnProperty) properties and concat into single string both property name and then ### and then value and then %%% in between.

Then enhance your object with property hash like:

myObj.hash = String.hashCode(StringOfNamesAndValues);

Now iterate trough your array using for, and compare obj.hash to objArray[index].hash

Once they match you fond your object, store the index :)

If your object and one in the array don't have to be EXACTLY the same object but only a subset needs to be same. Instead using all property names in hash generation, use only the names and values of properties you wanna to be same. Compare hashes made in that way - voila!

2.) More brutish way would be to make object equal function that takes 2 objects and compares all the properties and values of respective properties. Now iterate trough array using that function. Pass your object and array object as parameters. If it returns that comparison is true, store index.

The bigger the objects are the slower this works.The bigger array is the slower this works. The more time you search for same objects slower this works (you compare every time instead making hash once).

Also, if you are having a very large set of object, and search often but add or remove to it sparsely, consider ordering the array in order considering hash values. Then use binary tree search for that hash to find appropriate object instead iterating from start to end each time.

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