Verifying duplicate objects in array of objects using JavaScript

Question

I am having array of objects in a following form,

let test = [
{
 RowCreationMethod: "excel",
 deviceID: "123ECd9",
 deviceName: "ZENW42NLPC0378",
 devicePrimary: "Yes",
 deviceType: "Laptop",
 employeeID: 101,
 isExists: "No",
 isRescheduled: "No",
 vipUser: "Yes"
 },{
 RowCreationMethod: "excel",
 deviceName: "ZENW42NLPC0378",
 devicePrimary: "Yes",
 deviceType: "Laptop",
 deviceID: "123ECd9",
 employeeID: 101,
 isExists: "No",
 isRescheduled: "No",
 vipUser: "Yes"
 }];

I have written following code to check if their exits any duplicate object in my array its working but if I changes the sequence of any object properties then its not working, because in my code I am converting objects to string and verifying it.

Here is my code

let final = []
test.forEach(x => {
  if(!final.some(y => JSON.stringify(y) === JSON.stringify(x))){
    final.push(x)
  }
})

you could probably use JSON.stringify(Object.values(y).sort()). Worst-case: loop though the object properties and compare each to each. If you do that, run your existing JSON compare and sub-iterate only if false to keep it fast when possible. You can also use [].filter instead of forEach to collect the uniques w/o [].push(). — dandavis
– dandavis, Commented Jun 1, 2020 at 16:59
You can use Object.keys() to get an array of the keys in the objects. You can check if the array lengths are equal, and then check if their values in both objects match. — Taplar
– Taplar, Commented Jun 1, 2020 at 17:01
Will all the objects have the same set of keys or can they be missing? — adiga
– adiga, Commented Jun 1, 2020 at 17:02
all the objects are having same set of key but sequence in object is not same its random. — FaizanSyed
– FaizanSyed, Commented Jun 1, 2020 at 17:03

Unmitigated · Accepted Answer · 2020-06-01 17:16:07Z

For checking shallow equality, you can use Object.keys to get the keys of both objects, compare their lengths, and then check if each value is equal.

let test = [
{
 RowCreationMethod: "excel",
 deviceID: "123ECd9",
 deviceName: "ZENW42NLPC0378",
 devicePrimary: "Yes",
 deviceType: "Laptop",
 employeeID: 101,
 isExists: "No",
 isRescheduled: "No",
 vipUser: "Yes"
 },{
 RowCreationMethod: "excel",
 deviceName: "ZENW42NLPC0378",
 devicePrimary: "Yes",
 deviceType: "Laptop",
 deviceID: "123ECd9",
 employeeID: 101,
 isExists: "No",
 isRescheduled: "No",
 vipUser: "Yes"
 }];
 let final = [];
test.forEach(x => {
  if(!final.some(y => objectShallowEquals(x,y))){
    final.push(x);
  }
});
console.log(final);
function objectShallowEquals(obj1, obj2){
  const keys = Object.keys(obj1);
  const keys2 = Object.keys(obj2);
  if(keys.length != keys2.length) return false;
  for(const key of keys){
  	if(!(key in obj2) || obj1[key] !== obj2[key])return false;
  }
  return true;
}

If you aren't too worried about performance, you can use JSON.stringify on the entries of each object after sorting to compare them.

let test = [
{
 RowCreationMethod: "excel",
 deviceID: "123ECd9",
 deviceName: "ZENW42NLPC0378",
 devicePrimary: "Yes",
 deviceType: "Laptop",
 employeeID: 101,
 isExists: "No",
 isRescheduled: "No",
 vipUser: "Yes"
 },{
 RowCreationMethod: "excel",
 deviceName: "ZENW42NLPC0378",
 devicePrimary: "Yes",
 deviceType: "Laptop",
 deviceID: "123ECd9",
 employeeID: 101,
 isExists: "No",
 isRescheduled: "No",
 vipUser: "Yes"
 }];
 let final = [];
test.forEach(x => {
  if(!final.some(y => 
JSON.stringify(Object.entries(y).sort())===JSON.stringify(Object.entries(x).sort())
)) {
    final.push(x);
  }
});
console.log(final);

adiga · Accepted Answer · 2020-06-01 17:21:56Z

You could create a Set of every key in the array. Then, use reduce to group the array based on a unique value string for the each object. i.e. a string with the values of an object separated by | in the same order as allKeys. For example, for the given 2 objects, it will look like this:

"excel|123ECd9|ZENW42NLPC0378|Yes|Laptop|101|No|No|Yes"

If another object has the same string, it will be overwritten in the accumulator object.

This will work even if some objects have missing keys

var test=[{RowCreationMethod:"excel",deviceID:"123ECd9",deviceName:"ZENW42NLPC0378",devicePrimary:"Yes",deviceType:"Laptop",employeeID:101,isExists:"No",isRescheduled:"No",vipUser:"Yes"},{RowCreationMethod:"excel",deviceName:"ZENW42NLPC0378",devicePrimary:"Yes",deviceType:"Laptop",deviceID:"123ECd9",employeeID:101,isExists:"No",isRescheduled:"No",vipUser:"Yes"}];

function uniqueObjects(array) {
  const set = new Set(array.flatMap(Object.keys)),
        allKeys = Array.from(set);
        
  const group = array.reduce((acc, o) => {
    const unique = allKeys.map(k => o[k]).join('|');
    acc[unique] = o;
    return acc
  }, {})
  
  return Object.values(group)
}

console.log(uniqueObjects(test))

If every object has the same set of keys, you can skip the Set step and replace it with

const allKeys = Object.keys(array[0])

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