Set a Null Input to Zero

I'm guessing this question will be one of the easiest questions ever posted but I'm just not getting this fix. I have a simple Javascript program that calculates a users pace for their run. The inputs are done through an HTML Form.

The user can input hours, minutes, & seconds of their run. Then the distance number & measurment. Then finally the pace desired. I am having some trouble with null values in this program. If I input a 0 in hours and then fill everything out the program works great. 100%! But, if I leave the field blank and hit calculate I get a NaN. I'm guessing I need some kind of statement like if this value is null set it to zero but I am not having any luck with exactly what kind of syntax I need. So here is the code, again not very complex, any help would be greatly appreciated!


function calculateTime(){
var time_hour = parseInt(document.getElementById("time_hour").value);
var time_min = parseInt(document.getElementById("time_minute").value);
var time_sec = parseFloat(document.getElementById("time_second").value);
var dist_num = parseFloat(document.getElementById("dist_num").value);
var pace_choice = document.getElementById("pace_choice").selectedIndex;
var dist_choice = document.getElementById("dist_choice").selectedIndex;
var total_sec = (time_hour * 3600) + (time_min * 60) + (time_sec);

// Then I'm guessing my if statement would go here somewhere?

Here is the pace calculator! As you will see if you fill in all values everything works fine. But if you leave hour blank NaN

http://www.gmustudent.com/calc.html

This example should help:

var t = "";
parseInt(t); // NaN
parseInt(+t); // 0

Note that the unary "+" operator returns its operand transformed into a number.

This example should help:

var t = "";
parseInt(t); // NaN
parseInt(+t); // 0

Note that the unary "+" operator returns its operand transformed into a number.

So in order to do what you are saying should I replace t with time_hour in order to set it to 0?

Not quite.


var time_hour = parseInt(+document.getElementById("time_hour").value);

But you could also be more explicit about it:

var time_hour = parseInt(document.getElementById("time_hour").value);
if ( isNaN(time_hour) ) time_hour = 0;

Not quite.


var time_hour = parseInt(+document.getElementById("time_hour").value);

But you could also be more explicit about it:

var time_hour = parseInt(document.getElementById("time_hour").value);
if ( isNaN(time_hour) ) time_hour = 0;


WOW Thank you so much!!! This was my first question ever on a forum and it was awesome! Thank you again!