Efficient algorithm for grouping elements and counting duplicates in JavaScript

We have got an array of objects. If one property of the object is the same as in another object, we consider it to be a duplicate entry.

We want to group objects by this property and store information about how many times the "duplicate" occurred.

   X A B O
   Y X Z I
   Y X Z U
   X A B L
   Y X Z K

We want to group by the first value.

Another two properties are the same in each duplicate too, but comparing the first value will be enough.

We need to display to the user a result that looks like −

   Y X Z (3)
   X A B (2)

Example

The code for this will be −

const arr = [
   {x: 'x', acc: 'acc', val: 'val'},
   {y: 'y', x: 'x', z: 'z'},
   {y: 'y', x: 'x', z: 'z'},
   {x: 'x', c: 'c', val: 'val'}
];
const countOccurrence = (arr = []) => {
   const res = {};
   arr.forEach (item => {
      Object.keys( item ).forEach (prop => {
         ( res[prop] ) ? res[prop] += 1 : res[prop] = 1;
      });
   });
   return res;
}
const groupByOccurrence = (data = []) => {
   const obj = countOccurrence(data);
   const res = Object.keys ( obj ).reduce ( ( acc, val ) => {
      ( acc[obj[val]] ) ? acc[obj[val]].push ( val ) : acc[obj[val]] = [val];
      return acc;
   }, {});
   return res;
}
console.log(groupByOccurrence(arr));

Output

And the output in the console will be:
{ '1': [ 'acc', 'c' ], '2': [ 'val', 'y', 'z' ], '4': [ 'x' ] }

AmitDiwan

Published on 24-Nov-2020 10:40:12

• Related Questions & Answers
• Counting duplicates and aggregating array of objects in JavaScript
• Function for counting frequency of space separated elements in JavaScript
• Grouping an Array and Counting items creating new array based on Groups in JavaScript
• JavaScript: Adjacent Elements Product Algorithm
• Counting unique elements in an array in JavaScript
• Commons including duplicates in array elements in JavaScript
• Algorithm for matrix multiplication in JavaScript
• Counting smaller and greater in JavaScript
• Counting below / par elements from an array - JavaScript
• Counting common elements in MySQL?
• Outlook Tips and Tricks for Efficient Work Productivity
• Grouping and sorting 2-D array in JavaScript
• Grouping array of array on the basis of elements in JavaScript
• Euclidean Algorithm for calculating GCD in JavaScript
• Merge and remove duplicates in JavaScript Array