Jquery math within function

Question

I'm trying to multiply and input amount by 3.5%, Can anyone give me any ideas how to do it?

$("#invest_amount").keyup(function() {

         $('#fee').val($('#invest_amount').val() + 3.5);

        });

You write in your question that you want to multiply, yet you write + in your code instead of multiplication. — Jakob
– Jakob, Commented Dec 8, 2010 at 10:26

Nick Craver · Accepted Answer · 2010-12-08 10:18:14Z

4

You need to parse the input first then use * to multiply, not +, for example:

$("#invest_amount").keyup(function() {
  $('#fee').val(parseFloat($('#invest_amount').val()) * .035);
});

or...

$("#invest_amount").keyup(function() {
  $('#fee').val(+$('#invest_amount').val() * .035);
});

.val() returns a string, so you need to use + or praseFloat() to convert it to a number first

answered Dec 8, 2010 at 10:18

Nick Craver

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3 Comments

Charles Web Dev Over a year ago

Do you know how I can use .toFixed(2)with this? Its not working for me?

Nick Craver Over a year ago

@user534830 - like this: $('#fee').val((+$('#invest_amount').val() * .035).toFixed(2));

Andy E Over a year ago

If you're multiplying, there's actually no need to force the coercion with + because * will do it for you, e.g. $('#fee').val(($('#invest_amount').val() * .035).toFixed(2));

Darin Dimitrov · Accepted Answer · 2010-12-08 10:18:14Z

3

You need to parse the value first:

var value = parseFloat($('#invest_amount').val());
if (!isNaN(value)) {
    $('#fee').val(value * 0.035);
} else {
    alert('The entered value is not a valid number');
}

answered Dec 8, 2010 at 10:18

Darin Dimitrov

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Comments

charliegriefer · Accepted Answer · 2010-12-08 10:18:07Z

0

$( '#fee' ).val( $( '#invest_amount' ).val() * .035 );

answered Dec 8, 2010 at 10:18

charliegriefer

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Comments

John Sjölander · Accepted Answer · 2010-12-08 10:36:02Z

0

Knowing mathematics, and the significance of mathematical symbols, seems to be a basic prerequisite for your problem. Read more about mathematics here: http://en.wikipedia.org/wiki/Mathematics

answered Dec 8, 2010 at 10:36

John Sjölander

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