array-find-duplicates

Find duplicate values in an array

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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.