CODEWITHSUNDEEP
javascriptlodash
edencorbin
edencorbin

Reputation: 2929

lodash javascript array of duplicates that match multiple parameters

I have an array, to simplify lets say persons with first, last, and age. I want to make a new array of all persons that have the same first name, same last name and same age. For example my starting array:

[
  {id: 1, first: 'fred', last: 'smith', age: 21},
  {id: 2, first: 'fred', last: 'smith', age: 21},
  {id: 3, first: 'tom', last: 'smith', age: 21},
  {id: 4, first: 'fred', last: 'smith', age: 32}
]

I would like to return the duplicates that match first/last/age:

[
  {id: 1, first: 'fred', last: 'smith', age: 21},
  {id: 2, first: 'fred', last: 'smith', age: 21}
]

I'm struggling with _.uniq to figure out how to do this, any help is appreciated.

Upvotes: 2

Views: 91

Answers (1)

ryeballar
ryeballar

Reputation: 30088

You can make use of _.groupBy() to group values, make sure that it is grouped by values that you determine to be the criteria for a duplicate. You can then _.filter() each grouped values by the lengths of the arrays they accumulated and then _.flatten() it to obtain the final array. 

var data = [
  {id: 1, first: 'fred', last: 'smith', age: 21},
  {id: 2, first: 'fred', last: 'smith', age: 21},
  {id: 3, first: 'tom', last: 'smith', age: 21},
  {id: 4, first: 'fred', last: 'smith', age: 32}
];

var result = _(data)
  .groupBy(i => _(i).pick('first', 'last', 'age').values().value())
  .filter(i => i.length > 1)
  .flatten()
  .value();

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.11.2/lodash.js"></script>

Upvotes: 3

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