ServiceNow: Check for duplicates in an array

Use cases

Check if an array contains duplicate values

Options / Tools to achieve this

1. every()

2. some()

3. filter()

4. more will be added soon

How To - Details:

1. Use every() with indexOf()

/*
** @param (string) element - current element that is being processed in the array.
** @param (number) index - index of the current element being processed in the array.
** @param {array} arrValues - array of values
** return {Boolean} true if values are unique, false if it contains duplicates
*/
// Use Case 1: currently logged in user
var arrValues = ['test1', 'test2', 'test1'];

function isUnique(arrValues) {
  return isUniqueValues = arrValues.every(function (element, index, arrValues) { 
      // Check if there is any duplicate value 
    return arrValues.indexOf(element) === index; 
  });
}
isUnique(arrValues); // returns false in this case

2. Use some() with indexOf()

/*
** @description: Check if the array contains duplicates (if it finds more than one index for each value / element)
** @param (string) element - current element that is being processed in the array.
** @param {array} arrValues - array of values
** @returns {boolean} - true if it contains duplicates
*/
var arrValues = ['test1', 'test3', 'test1'];
function containsDuplicates(arrValues) {
  var result = arrValues.some(function (element) {
    return arrValues.indexOf(element) !== arrValues.lastIndexOf(element);
  });
  return result;
}
containsDuplicates(arrValues);

3. Use filter() with indexOf()

var arrValues = ['test1', 'test3', 'test1'];

function fetchDuplicates(arrValues ) {
 return arrValues.filter(function(item, index) {
 return arrValues.indexOf(item) !== index});
}
var hasDuplicates = fetchDuplicates(arrValues ).length > 0 ? true : false;

Test this in a Background Script or in Xplore:

Of course you can also return the value that has a duplicate / is not unique:

Useful links

• mdn web docs - Array.prototype.every()

• freecodecamp - every and some - array methods in javascript