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

Assuming all you want is to detect how many duplicates of 'test0' are in the array. I guess an easy way to do that is to use the join method to transform the array in a string, and then use the match method.

var arr= ['test0','test2','test0'];
var str = arr.join();

console.log(str) //"test0,test2,test0"

var duplicates = str.match(/test0/g);
var duplicateNumber = duplicates.length;

console.log(duplicateNumber); //2