Is there a way to determine if the items in an array are duplicated?

Hello all, as a beginner in coding, I'm looking for guidance on determining whether an array contains repeated objects regardless of their order, without knowing the specific objects in advance. Let's say:

I initialize an empty array:

var random_array = [];

Then, using a function to add objects to the array, it becomes:

var random_array = [ball, ball, tree, ball, tree, bus, car];

In this array:

There are 3 balls, 2 trees, 1 bus, and 1 car.

How can I identify these repetitions? Should a for loop be used or another approach? I'm new to coding, so any help is appreciated. Thank you!

Edit:

Here is a basic code snippet I have been working on:

function Product(name, price) {
    this.name = name;
    this.price = price;
}

var register = {
    total: 0,
    list: [],

    add: function(Object, quant) {
        this.total += Object.price * quant;
        for (x=0; x < quant; x++) {
        this.list.push(Object);
        }
    },

undo: function() {
    var last_item = this.list[this.list.length - 1];
    this.total -= last_item.price;
    this.list.pop(this.list[this.list.length - 1]);
    },

print: function() {
    console.log("Super Random Market");
    for (x = 0; x < this.list.length; x++) {
        console.log(this.list[x].name + ": " + this.list[x].price.toPrecision(3));
    }
    console.log("Total: " + this.total.toFixed(2));
    }
}

var icecream_1 = new Product("Chocolate Icecream", 2.30);
var cake_1 = new Product("Chocolate cake", 4.00);

register.add(icecream_1, 5);
register.add(cake_1, 3);

register.print();

I am attempting to create a cash register system and am exploring how to display items with quantities only once, rather than multiple times.

Answer №1

const itemsArray = ["ball", "ball", "tree", "ball", "tree", "bus", "car"];
const itemCountObject = {};

itemsArray.forEach(function(item){
    if(item in itemCountObject) {
        itemCountObject[item] = itemCountObject[item] + 1;
    } else {
        itemCountObject[item] = 1;
    }
});

If you want to check the number of occurrences of "ball" in the array, you can do so like this: itemCountObject.ball, which will give you a count of 3.

See it in action on JSFiddle: http://jsfiddle.net/3XpXn/2/

A more concise version:

const itemsArray = ["ball", "ball", "tree", "ball", "tree", "bus", "car"],
    itemCountObject = {};

itemsArray.forEach(function(item){
    item in itemCountObject ? itemCountObject[item] = itemCountObject[item] + 1 : itemCountObject[item] = 1;
});

Answer №2

This code snippet is designed to efficiently count the unique elements in an array.

    var fruitsArray = ["apple", "apple", "orange", "apple", "banana", "orange", "kiwi"];       
        Array.prototype.countUniqueElements = function(){
          var counts = {}, index;   
          for (index = 0; index < this.length; index++) {    
             counts[this[index]] = (counts[this[index]] || 0) + 1;
            }  
          return counts;
        };
console.log(fruitsArray.countUniqueElements());//{ apple: 3, orange: 2, banana: 1, kiwi: 1 } 

To see this code in action, you can visit the following URL:

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