How to sum input numbers and database values in javascript

Question

I have appended data and I print each data price in hidden input. Now I want to sum these prices with input numbers as quantity in order to get the total amount but nothing prints.

Code

javascript

success:function(data) {
        //append data to my view
        data.forEach(function(row) {
            var $meto = '';
            $meto += '<div class="col-md-3 mt-2">'+
                '<div class="card">'+
                    '<div class="card-body">'+
                        '<img src="{{url("images")}}/'+row['photo']+'" class="menuimg img-fluid" alt="image">'+
                        '<p>'+row['name']+'</p>'+
                        '<input type="number" name="qty[]" class="qty form-control">'+
                        '<input type="hidden" class="price" value="'+row['price']+'" />'+
                    '</div>'+
                '</div>'+
            '</div>';
            $('.here').append($meto);

            //sum prices
            $('.qty').on('keyup',function(){
                var qty = $('.qty').val();
                var price = $('.price').val();
                $("#total").html(qty*price);
            });
        });
}

html

<div class="col-md-10">
  <div class="row here"></div>
</div>
<p>Total: <span id="total"></span></p>

Explanation

I have filled 2 of my items with quantities 1 & 3 there is hidden input under each of them that holds their prices (as this sample they are 5000 & 16000)

Basically I should have something like this in my total div:

1*5000 = 5000
3*16000 = 48000
Total = 53000

However, it only gets my first input and ignores the rest. Any ideas?

question/hint: what happens if I run $(".price").val(10); in my console? Can I eat for a Total of 40 at your place, or do we have an issue? — Thomas
– Thomas, Commented Feb 12, 2019 at 8:02
@Thomas ok i got it now :) then you give me idea? my prices are coming in data loop and my sum function is out of that loop, how can I access those prices without printing them in hidden input? — mafortis
– mafortis, Commented Feb 12, 2019 at 8:08
I don't know how exactly your site works, but having the price that exposed in the frontend provides way to much attack surface. You have the price in a hidden input, do you send it to the backend? does the backend check the price it got sent or does it just accept it as truth? What if I have a screenshot of your page showing Total = 7500 but you charge me 15000 what's the legally binding price? Do you have to sell xy to me for 7500 because that was the price you showed me? ... and more stuff like that — Thomas
– Thomas, Commented Feb 12, 2019 at 8:09
@Thomas I see, I just paid attention to that and saw my sum function is actually inside my data loop, is there anyways I can pass that `row['price'] into my sum function? so i calculate it in there instead of getting it from input? — mafortis
– mafortis, Commented Feb 12, 2019 at 8:14

Rakesh Makluri · Accepted Answer · 2019-02-12 07:54:56Z

1

You are not adding all items prices. You need to loop through all items and calculate total.

Note: keep this after your forEach statement. Try this:

$('.qty').on('keyup',function() {
    var quantities = $('.qty');
    var prices = $('.price');
    var total = 0;
   $.each(quantities, (index, qty) => {
        total += parseInt($(qty).val() || 0) * parseFloat($(prices[index]).val() || 0) 
    });
    $("#total").html(total);
});

edited Feb 12, 2019 at 7:54

answered Feb 12, 2019 at 7:36

Rakesh Makluri

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6 Comments

mafortis Over a year ago

thanks, it returns TypeError: quantities.forEach is not a function

Rakesh Makluri Over a year ago

Updated the answer, check now.

mafortis Over a year ago

it says TypeError: qty.val is not a function

Rakesh Makluri Over a year ago

can you check now.

mafortis Over a year ago

there is some issues i made you small video i thought it could explain better streamable.com/y1csy

|

MrMaavin · Accepted Answer · 2019-02-12 07:42:05Z

0

I think the problem is, that you cant get the value from multiple elements with the function ".val()". You only can get multiple values from one element.

You need another function to do want you want to achieve.

You should have a look here: Stackoverflow Question

Anway - you should not save prices into hidden html elements in production environments.

edited Feb 12, 2019 at 7:42

MrMaavin

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answered Feb 12, 2019 at 7:37

Hannes

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1 Comment

mafortis Over a year ago

hi, sorry i didn't get that map function, it only gets the inputs where do I calculate them?

varun agarwal · Accepted Answer · 2019-02-12 08:04:25Z

0

Iterate over the parent element to find the exact price and quantity for each element.

$('.qty').on('keyup',function(){
    var total = 0;
    $('.card-body').each(function(){
        var qty = parseFloat($(this).find('.qty').val());
        if (!qty) return;
        var price = parseFloat($(this).find('.price').val());
        total += (qty * price);
    });
    $("#total").html(total);
});

Attaching a Fiddle

edited Feb 12, 2019 at 8:04

answered Feb 12, 2019 at 7:44

varun agarwal

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3 Comments

mafortis Over a year ago

it has 2 issues, 1 it can't get if i only fill one item quantity (must be multiple) 2 it sum wrong.

varun agarwal Over a year ago

Edited it, hadn't handled the case where the quantity is null.

varun agarwal Over a year ago

Check the fiddle attached, I have added dummy data and used the function to demonstrate the total

score 0 · Accepted Answer · 2019-02-12 08:14:16Z

I don't know jQuery, though I can help you with vanilla JS.

The problem here is:

$('.qty').on('keyup',function(){
            var qty = $('.qty').val();
            var price = $('.price').val();

            $("#total").html(qty*price);
         });

This is setting an event listener only for the first .qty, even though there are many of them. So, you should select and iterate over them all, just like you did with the data:

let qtyNodes = document.querySelectorAll('.qty');
let priceNodes = document.querySelectorAll('.price');

let outputNode = document.querySelector('#total');
let sum = 0;

qtyNodes.forEach(function(qtyNode) { // Set event listener to every single qty node 

    qtyNode.addEventListener('keyup', function() {

        qtyNodes.forEach((qtyNode, index) => { // Calculate final price, using each meal price per quantity value.
            sum = qtyNode.value * priceNodes[index].value;
        })

    });

})

outputNode.innerHTML = `${sum}`;

It is important that you keep the arrays-like (qtyNodes and priceNodes) outside the given loop, as it will be accessing the DOM at each iteration and will demand too much performance. Placing it outside, you will access the DOM only one time.

Also, note that: you should be using "input" event, as opposed to "keyup". Input events will fire as soon as the user insert any data, just like a combination of "keyup" and "keydown".

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