Using lodash to check whether an array has duplicate values

Question

What do you all think would be the best (best can be interpreted as most readable or most performant, your choice) way to write a function using the lodash utilities in order to check an array for duplicate values.

I want to input ['foo', 'foo', 'bar'] and have the function return true. And input ['foo', 'bar', 'baz'] and have the function return false.

Answer 1

You can try this code:

function hasDuplicates(a) {    return _.uniq(a).length !== a.length;   }    var a = [1,2,1,3,4,5];  var b = [1,2,3,4,5,6];    document.write(hasDuplicates(a), ',',hasDuplicates(b));

<script src="http://cdnjs.cloudflare.com/ajax/libs/lodash.js/3.1.0/lodash.min.js"></script>

Answer 2

As of ES6 you can simply use Set so this becomes:

let hasDuplicates = arr => new Set(arr).size != arr.length    console.log(hasDuplicates([5,3,2,1,2,1,2,1]))  console.log(hasDuplicates([1,2,3,4,5]))

Which somewhat negates the use of lodash in this particular case.