Working with Operators and Expressions - HTML, CSS, and Dynamic HTML - page 793

Figure 11-25 displaying the integer number of hours left in the day

integer number of
hours left in the day

jbdphotography/Shutterstock.com

The technique to calculate the minutes left in the current hour is similar to the one
you used to calculate the hours left in the current day. You multiply the difference
between the hours value and the whole hours value by 60 (the number of minutes in
an hour) to express the fractional part in terms of minutes, as shown in the following
command:

var minutes = (hours - Math.floor(hours))*60;

Finally, to calculate the seconds left in the current minute, you multiply the fractional
part of the minutes variable by 60 (the number of seconds in a minute), as follows:

var seconds = (minutes - Math.floor(minutes))*60;

As with the days and hours variables, you want to display only the integer part of the
minutes and seconds variables by using the Math.floor() method. You'll add these
commands to the NYClock() function.

To calculate the minutes and seconds left:

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1. Return to the clock.htm file and the NYClock() function in your text editor.

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2. Below the statement that sets the value of the hrsLeft field, insert the following lines:

// calculate the minutes left in the current hour
var minutes = (hours - Math.floor(hours))*60;

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3. Change the statement that sets the value of the minsLeft field to:

// display minutes rounded to the next lowest integer
document.clockform.minsLeft.value = Math.floor(minutes) + “
minute(s)”;

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4. Below the statement that sets the value of the minsLeft field, insert the
following lines:

// calculate the seconds left in the current minute
var seconds = (minutes - Math.floor(minutes))*60;

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5. Change the statement that sets the value of the secsLeft field to:

// display seconds rounded to the next lowest integer
document.clockform.secsLeft.value = Math.floor(seconds) + “
second(s)”;