Calculating price from quantity

Question

I making the shops for my site, and but I can't understand why this conde don't wont to work...Here's the code:

<script>
function Price() {
    var Quantity = document.getElementsByClassName('BUY')[0].value;
    var Total = Quantity * 20;
    if (!IsNan(Total)) {

        document.getElementsByClassName('Total').innerHTML = Total;
        document.getElementsByClassName('Quantity').innerHTML = Quantity;
    } else {
        document.getElementsByClassName('Total').innerHTML = "Invalid number";
        document.getElementsByClassName('Quantity').innerHTML = 0
    }
}

Here is the html:

<input style="margin-top:1%;" type="text" name="BUY" class="input" maxlength="1000" autocomplete="on" placeholder="Buy " onchange="Price()" required>Price for <span class="Quantity">0</span>Views:<span class="Total">0</span> Satoshis<br>

From this code I expect a print of the calculation based on the quantity but the code don't work and I get no errors...

"Won't work" is not a useful problem statement. What doesn't work exactly? — Federico klez Culloca, Dec 07 '17 at 14:48
maybe you should use `parseInt(Quantity)` before multiplying? — Dan Cantir, Dec 07 '17 at 14:49
missing `parseInt` around `Quantity` (value returns string). Undefined element with `class="BUY"`. Collection of elements (`byClassName`) has no `.innerHTML` method. Etc. — pavel, Dec 07 '17 at 14:50
Your input is text. Make sure all your variables are actually numbers before preforming math operations on them (TL;DR- They are not on your case) — Idan Beker, Dec 07 '17 at 14:50
@FedericoklezCulloca: in this code nothing, there are a lot of basic mistakes — pavel, Dec 07 '17 at 14:51
Please do some basic debugging, that will solve many of the small mistakes here — Sterling Archer, Dec 07 '17 at 14:51
If it's not too late, I'd advise you against using the same text you display to users as source for maths and calculations of any sort. You should always keep your number in properly typed variables and convert the result to text for mere display purposes. — Álvaro González, Dec 07 '17 at 15:11

score -1 · Answer 1 · answered Dec 07 '17 at 14:54

-1

document.getElementsByClassName('BUY') will search for elements having class 'BUY', but ur input has class 'input'

answered Dec 07 '17 at 14:54

Nizar Ahmed

180
9

jasinth premkumar · Accepted Answer · 2017-12-07T16:02:50.013

you have worng class name in the script that's why it is not working.

corrected code:(Just copy & paste it .works changed class into ID) Because using classname it is not fetching the correct value instead it assigns Quantity as undefined refer this answer

                function price(){
                    var Quantity=document.getElementById('buy').value;
                    
                    var Total=Quantity*20;
                    if(Total != 'NaN'){
    
                        document.getElementById('Total').innerHTML=Total;
                        document.getElementById('Quantity').innerHTML=Quantity;
                    }else{
                        document.getElementById('Total').innerHTML="Invalid number";
                        document.getElementById('Quantity').innerHTML=0;
                    }
                }

<input style="margin-top:1%;" type="text" name="BY" id="buy" maxlength="1000" autocomplete="on" placeholder="Buy " onkeyup="price()" required/>Price for 
    <span id="Quantity">0</span>
    Views:<span id="Total">0</span>
    Satoshis<br>

hey, *man*, I didn't downvote you, but if an answer doesn't solve the problem it gets downvoted. This case is particular in that, since OP didn't do any basic debugging, you have to correct *a lot* of stuff. Good luck. — Federico klez Culloca, Dec 07 '17 at 14:58
Also, don't complain, it isn't *manly*. If you correct your question and solve everything, chances are the downvoter will retract their downvote. EDIT: if it was not clear, I'm using "man" a lot because you did first, and I'm just teasing — Federico klez Culloca, Dec 07 '17 at 14:58

Calculating price from quantity

2 Answers2