Mongodb how to remove duplicate entries in arrays

run.js

// http://codingtricks.fidibuy.com/participant/join/5474b4eab7606ef9d71c045a/MongoDb:-how-to-remove-duplicate-entries-in-arrays
// with modification

// MongoDB GUI Tools: https://studio3t.com/download

var fixFieldName = "primary_images";
var collectionName = "my_collection";

db[collectionName].find({
    "_id": ObjectId("5762a2d397694a5295176697")
}).forEach(function(elem) {
    var newArrays = [];
    var newArraysMap = {};

    for (var i = 0; i < elem[fixFieldName].length; i++) {
        if (!newArraysMap[elem[fixFieldName][i]]) {
            newArraysMap[elem[fixFieldName][i]] = elem[fixFieldName][i];
            newArrays.push(elem[fixFieldName][i]);
        }
    }
    elem[fixFieldName] = newArrays;
    db[collectionName].save(elem);
    printjson(elem);
})