array-find-duplicates

Find duplicate values in an array.

By default, array-find-duplicates uses strict equality (===) to determine duplicates.

An optional comparison function can be passed and will be used instead of strict equality when checking for duplicates

O(n log n) complexity.

Example

npm install array-find-duplicates

With default comparison

const findDuplicates = require('array-find-duplicates');

const array = ['a', 'b', 'b', 'c'];
const duplicates = findDuplicates(array);
console.log(duplicates);
// expected output: ['b', 'b']

With supplied compare function

const findDuplicates = require('array-find-duplicates');

const array = [
  { id: 1, content: 'foo' },
  { id: 2, content: 'bar' },
  { id: 2, content: 'baz' }
];
const duplicates = findDuplicates(array, (a, b) => a.id === b.id);
console.log(duplicates);
// expected output: [{ id: 2, content: 'bar' }, { id: 2, content: 'baz' }]

Syntax

findDuplicates(array[, compareFunction(firstEl, secondEl)])

Parameters

• array: array to search for duplicates.
• compareFunction Optional: function to execute on a pair of elements to determine equality. If it returns true, the elements are considered to be duplicates. If no compare function is supplied, findDuplicates uses strict equality to determine duplicates.
  • firstEl: first element for comparison.
  • secondEl: second element for comparison.

Return value

• Returns a new array containing each instance of all duplicate values in the original array.

Testing

Uses jest

npm run test

License

This package is licensed under The MIT License.