Find number a duplicates and it's name in array of objects

Question

I want to find number a duplicates and it's name in array of objects in javascript.

I checked related questions but none help in finding the exact duplicate count. Even they do not focus on finding it if there are multiple duplicates

I tried this which will throw message on finding duplicates. But i want the count of duplicates and handle the case when there are multiple duplicates with count of each name occuring multiple times.

My code:

let keyArr = this.customPropertiesArray.map(function (item: any) { return item.name });
 let isDuplicate = keyArr.some(function (item: any, idx: any) {
      return keyArr.indexOf(item) != idx
 });
 if (isDuplicate) {
     console.log("Duplicate found");
 }

The array could be something like this:

let array=[
{"name":"name1","value":"value1"},
{"name":"name2","value":"value2"},
{"name":"name1","value":"value42"},
{"name":"name2","value":"value52"},
{"name":"name3","value":"value2"},
{"name":"name2","value":"value2"}...];

I want a message something like "name1 is duplicate occuring 2 times" and "name2 is duplicate occuring 3 times"

Yes I want it to be supported in majority of browsers. Just in case if you are using any new features of javascript. — vulcan
– vulcan, Commented Apr 28, 2017 at 7:10

Nina Scholz · Accepted Answer · 2017-04-28 07:15:17Z

1

You could just count the names in an object.

var array = [{ name: "name1", value: "value1" }, { name: "name2", value: "value2" }, { name: "name1", value: "value42" }, { name: "name2", value: "value52" }, { name: "name3", value: "value2" }, { name: "name2", value: "value2" }],
    count = Object.create(null);

array.forEach(function (o) {
    count[o.name] = (count[o.name] || 0) + 1;
});

Object.keys(count).forEach(function (k) {
    if (count[k] > 1) {
        console.log(k + ' is duplicate occuring ' + count[k] + ' times.');
    }
});

console.log(count);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Apr 28, 2017 at 7:15

Nina Scholz

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Comments

dashton · Accepted Answer · 2017-04-28 14:41:40Z

0

This will list your duplicates:

let array=[
{"name":"name1","value":"value1"},
{"name":"name2","value":"value2"},
{"name":"name1","value":"value42"},
{"name":"name2","value":"value52"},
{"name":"name3","value":"value2"},
{"name":"name2","value":"value2"}];

const counts = array.reduce((accum, current) => {
  accum[current.name] = (accum[current.name] || 0) + 1;
  return accum;
}, {});

Object.keys(counts)
  .filter(key => counts[key] > 1)
  .forEach(grp => console.log(`${grp} is duplicate occurring ${counts[grp]} times`));

answered Apr 28, 2017 at 14:41

dashton

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