JavaScript count the duplicates in an array 
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                    I found this easiest 3 line to code to count duplicates in an array and it works.
Solution Count Duplicates In An Array
var elements = ["apple", "apple", "orange", "apple", "banana"];
var counts = {};
elements.forEach(function(x) {
    counts[x] = (counts[x] || 0)   1;
});
document.write("Apple: "   counts.apple   "<br/>");
document.write("Banana: "   counts.banana   "<br/>");
document.write("Orange: "   counts.orange   "<br/>");