Benchmark: non-unique-elements

Tests:

Count
var data = [6, 1, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 5, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 8]; var cnt = {}; data.forEach(d => cnt[d] ? cnt[d]++ : cnt[d]=1); data.filter(d => cnt[d] > 1);
IndexOf
var data = [6, 1, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 5, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 2, 3, 1, 3, 8]; data.filter(d => data.indexOf(d) != data.lastIndexOf(d));

Rendered benchmark preparation results:

Previous results

Test case name	Result
Count
IndexOf

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Latest run results:

Run details: (Test run date: 7 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36

Browser/OS: Chrome 53 on Windows

Test name	Executions per second
Count	112172.4 Ops/sec
IndexOf	125256.0 Ops/sec

non-unique-elements (version: 0)