Real Time Javascript Calculation Based On Form Inputs

Question

I'm trying to make a real-time calculator based on form inputs, when I use a sample div it works but I seem to be missing something when I try to print the total inside an input...

Working Markup Solution:

 <input id='first' type="text" class="form-control formBlock" name="bus_ticket"  placeholder="Bus Ticket..." required/><br />

<input id='second' type="text" class="form-control formBlock" name="plane_ticket"  placeholder="Plane Ticket..." required/><br />

<input id='third' type="text" class="form-control formBlock" name="hotel_expenses"  placeholder="Hotel Expenses..." required/><br />

 <input id='fourth' type="text" class="form-control formBlock" name="eating_expenses"  placeholder="Eating Expenses..." required/><br />

Total : <span id="total_expenses"></span>

Working Script

$('input').keyup(function(){ // run anytime the value changes


    var firstValue = parseFloat($('#first').val()); // get value of field
    var secondValue = parseFloat($('#second').val()); // convert it to a float
    var thirdValue = parseFloat($('#third').val());
    var fourthValue = parseFloat($('#fourth').val());

    $('#total_expenses').html(firstValue + secondValue + thirdValue + fourthValue); // add them and output it
});

Non-Working Markup

<input id='total_expenses' type="text" class="form-control formBlock" name="funding"  placeholder="Total Expenses..."/>

Non-Working Script

$('input').keyup(function(){ // run anytime the value changes
    var firstValue = parseFloat($('#first').val()); // get value of field
    var secondValue = parseFloat($('#second').val()); // convert it to a float
    var thirdValue = parseFloat($('#third').val());
    var fourthValue = parseFloat($('#fourth').val());
    document.getElementById('#total_expenses').value(firstValue + secondValue + thirdValue + fourthValue);
// add them and output it
});

ITWitch · Accepted Answer · 2017-03-11 07:08:52Z

9

Here's a working JSFiddle.

You've been confusing Javascript and jQuery codes.

// Wrong code:
document.getElementById('#total_expenses').value(sum)
//Correct code:
document.getElementById('total_expenses').value() = sum

Also, change parseFloat to Number so you don't get NaN when at least one of your input fields is blank.

BONUS: change your <input type="text" /> to <input type="number" /> to prevent "non-numerical" inputs.

edited Mar 11, 2017 at 7:08

answered Mar 11, 2017 at 2:51

ITWitch

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3 Comments

Sebastian Farham Over a year ago

Very neat. Thank you.

ITWitch Over a year ago

I'm glad I could help :)

bharat savani Over a year ago

Good neat and clean solution @ITWitch

bharat savani · Accepted Answer · 2017-03-11 02:38:00Z

1

You can try this jquery code

var totalValue = firstValue + secondValue + thirdValue + fourthValue;
$('#total_expenses').val(totalValue);

answered Mar 11, 2017 at 2:38

bharat savani

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Comments

Pejka · Accepted Answer · 2017-03-11 02:45:21Z

1

First, when using getElementById you can omit the #. Secondly, assigning a value to an input using vanilla JS is done by simple assignment, and not a function call. So that line should look like this:

document.getElementById('total_expenses').value = firstValue + secondValue + thirdValue + fourthValue;

answered Mar 11, 2017 at 2:45

Pejka

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Here's a working JSFiddle.

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