fastest way to detect if duplicate entry exists in javascript array?

Question

var arr = [\'test0\',\'test2\',\'test0\'];

Like the above,there are two identical entries with value \"test0\",how to check it most efficiently?

Answer 1

If you sort the array, the duplicates are next to each other so that they are easy to find:

arr.sort();
var last = arr[0];
for (var i=1; i