Find dupes in JS array no comments

dupesInJsArrayNoComment.js

var cached = {};
var allTags = ["red", "pants", "jeans", "red", "black", "jeans", "black", "pants", "jeans"];
var duplicatedTags = [];

for (var i=0;i<allTags.length; i++) {
  if (cached[allTags[i]] == undefined) {
    
    cached[allTags[i]] = allTags[i];
    
    if (hasDup(allTags, allTags[i], allTags.length)) {
      duplicatedTags.push(allTags[i]);
    }
    
  }
}

// duplicatedTags now contains ["jeans"]
// You know that the 3 images you selected to edit tags all contain 'jeans' as a tag
console.log(duplicatedTags);

function hasDup(arr, val, greaterThan) {
  
    var count = 0;
    
    for (var i = 0; i < arr.length; i++) {
        if (arr[i] == val)
            count++;
    }
    
    if (count >= greaterThan){
        return true;
    }
    
    return false;
}