PAWDD E-Training
17May/101

Increment and Decrement Operator

As you have probably thought prior to coming here, "I wish there was a way to increase or decrease a number without the need to use plus and minus operators over and over." Well if that was what your were thinking, then your idea has been realized with PHP "++"Increment and "--"Decrement.

This works the same in PHP and in JavaScript!

The way all this works is that normally to increase or decrease a number by one, you would need to do the following:

++/- - Pre-Increment / Decrement

<?php
 
$a = 10; 
//we need to increase $a by 1, normally we would do the following...
$a = $a + 1; // $a is now 11
 
//we need to decrease $a by 1, normally we would do the following...
$a = $a - 1; // $a is now 9
 
//There is a better way
$b = 10;
++$b //$b = 11 because we Incremented it by 1 first, by using the Increment operator "--" then returned its value
--$b //$b is 10 again because we first decremented it by 1 using the decrement operator "--" then returned its value
 
//The value of $b has literally changed, since the operator appeared prior to our variable
 
?>

With the above example showing how to increment and decrement a number by one, there is a little bit of a tricky situation happening behind the scenes. Since we placed the increment and decrement operator prior to the variable, in actuality behind the scenes PHP parser see the following :

PHP sees ++$a or --$a and literally, what takes place is that the PHP parser takes the value of $a and increments or decrements it by one, and then returns the value of $a incremented or decremented. The value of $b has literally changed, since the operator appeared prior to our variable, and that altered variable is then applied immediatly

However, in the following example something a little different takes place... Consider the following example where we move the increment/decrement operator after the variable we are working with.

Post-Increment / Decrement ++/- - 

<?php
 
$a = 10; 
//we need to increase $a by 1, normally we would do the following...
$a = $a + 1; // $a is now 11
 
//we need to decrease $a by 1, normally we would do the following...
$a = $a - 1; // $a is now 9
 
//There is a different way with different results than the prior example
 
$b = 10;
echo $b++; //what will echo is 10, however if we echo it again it will show 11
echo $b //will be 11 because it was echoed after it was incremented
 
echo $b--; //what will echo is 10, however if we echo it again it will show 9
echo $b //will be 9 because it was echoed after it was decremented
 
?>

The returned value for $b remains as it was prior to the operator acting upon it because the variable $b appears prior to the operator. Since the operator is after the variable it then makes the value chang, and when we use it a second time, it has the altered value because the operator took place after the variable.

Therefore, to make it clear; placing the operator prior to the number makes PHP act upon the variable prior to returning it. Otherwise, if the operator is placed after the variable, PHP acts upon the variable after its value is returned, meaning it returns the initial value first, and is then acted upon. Therefore, the second usage of the variable is where the alteration is noticed when the operator is placed after the variable.

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24Sep/091

JavaScript Out of Office Script

Hello again.  I have completed my very first functional JavaScript program.  Even though this program is simple in its approach, it is functional and will display anywhere you want, whether or not you are in your office.

I have created this script to change the color of the text to green when you are in the office, and to red when you are not.  This could be modified so that it changes the color of a specific division to your color of choice, or not to change the background color at all.

The appropriate message and color is displayed depending on your office hours. The following office hours were used as a guide:

Monday + Wednesday:      3:30pm-5:00pm
Tuesday + Thursday:   2:00pm-4:00pm
Friday:   1:00pm-4pm
Saturday + Sunday:      Out of the office

Here is the code in action, it will display only a simple message and will display the message and color inside of a H1 tag , the message will be appropriately displayed whether I am in my offce or not regarding the hours above... Please remember these hours from above are NOT my office hours, they are fictitious.

Where am I?

--------------------------------------------------------------- 

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Download the code as a zipped file: JavaScript Office Hours Script

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<script language = "JavaScript" type = "text/javascript">
	<!--
		var hours; 	//holds the determined hour of the day
		var minutes; //is the minutes
		var dow; //holds the day of the week
		var region; //holds the region of the day
		var outcome; //holds the outcome for the region
		var Now; //uses the date constructor to create a date object
		var openTime; //holds the time I will be in the office next
		var backgroundColor;  //holds our background color
		var message; //holds our message
		var nextTime; //holds our "next time" I will be in the office
		var outTime; //holds the time I leave the office
		var textColor;
 
 
		Now = new Date(); //creates the "Now" date object and assigns its value to variable "Now"
 
		hours = Now.getHours(); //retrieves and stores the hours from the "Now" date object
		minutes = Now.getMinutes(); //retrieves and stores the minutes from the "Now" date object
		dow = Now.getDay(); //retrieves and stores the "day of the week" from the "Now" date object
		textColor = backgroundColor;
 
		//starts the determination of what region of the week we are in via a "time" relationship
		if (hours < 13) { //0:00-12:59
			region = "A";
			}
		else if (hours < 14) { //13:00-14:00
			region = "B";
			}
		else if ( (hours == 14)||((hours == 15) && (minutes < 30)) ) { //14:00 or 15:00-15:29
			region = "C";
			}
		else if (hours < 16) {//15:30-15:59 - Could also be ((hours == 15) && (minutes >=30)) - but we don't need it due to we already eliminated the previous 29 minutes of the 15th hour
			region = "D";
			}
		else if ((hours == 16) && (minutes < 30)) { //16:00-16:29
			region = "E";
			}
		else if (hours < 17) { //16:30-16:59
			region = "F";
			}
		else {//region must be "G" - 17:00-23:59
			region = "G";
			}	
		//  Un-comment the line below to write the region to the screen for testing		
		//  document.writeln ("<h1>" + region + "</h1>");
 
 
		//determines the outcome based on a "dow" and "region" relationship
		if ( ((dow == 1) && (region == "G")) || ((dow == 2) && ((region == "A")||(region == "B"))) ) {
			outcome = 3; 
			}
		else if ( ((dow == 3) && (region == "G")) || ((dow == 4) && ((region == "A")||(region == "B"))) ) {
			outcome = 5;
			}
		else if ( ((dow == 2) && (region >= "E")) || ((dow == 3) && (region <= "C")) ) {
			outcome = 4;
			}
		else if ( ((dow == 4) && (region >= "E")) || ((dow == 5) && (region == "A")) ) {
			outcome = 6;
			}
		else if ( (( dow == 6) || (dow == 0)) || ( ((dow == 5) && (region >= "F")) || ((dow == 1) && (region <= "C")) ) ) {
			outcome = 2;
			}
		else{
			outcome = 1;
			}	
		//  Un-comment the line below to write the outcome to the screen for testing		
		//  document.writeln ("<h1>" + outcome + "</h1>");
 
 
		// start open varible set based on the "outcome"
		if (outcome == 1)
			openTime = true;
		else 
			openTime = false;
 
 
		//set messages for office times preceeding the current time via the "outcome"
		if (outcome == 1)
			nextTime = "";
		else if (outcome == 2)
			nextTime = "Monday at 3:30pm";
		else if (outcome == 3)
			nextTime = "Tueday at 2:00pm";
		else if (outcome == 4)
			nextTime = "Wednesday at 3:30pm";
		else if (outcome == 5)
			nextTime = "Thursday at 2:00pm";
		else //outcome must be 6
			nextTime = "Friday at 4:30pm";
 
 
		//determine outTime via a "outcome" and "dow" relationship
		if ( (outcome == 1) && (dow == 1) )
			outTime = "5:00pm";
		else if ( (outcome == 1) && (dow == 2) )
			outTime = "4:00pm";
		else if ( (outcome == 1) && (dow == 3) )
			outTime = "5:00pm";
		else if ( (outcome == 1) && (dow == 4) )
			outTime = "4:00pm";
		else if ( (outcome == 1) && (dow == 5) )
			outTime = "4:30pm";
		else //outTime must be nothing because it is Saturday or Sunday
			outTime = "";
 
 
		// start message variable set
		if (openTime) {
			backgroundColor = "#00FF00";
			message = "<h1 style=\"color:#0F0\">" + "I am in my office," + "<br />" + "I will be in my office until " + outTime + "</h1>";
			}
		else {
			backgroundColor = "#FF0000";
			message = "<h1 style=\"color:#F00\">" + "I am out of the office." + "<br />" + "The next time I will be in is: " + nextTime + "</h1>";
			}				
 
 
		//write the results to the screen with backgroundColor changing
		document.bgColor = "#516c82";				
		document.writeln (message);
 
 
 
 
		//  success at my first JavaScript program is sweet beautiful bliss :)  
	//-->
</script>
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24Sep/090

JavaScript E-Training

JavaScript PAWDD E-Training.

I am a proficient begenning JavaScript programmer for the web.  i have had wonderful teachers at my college.  I will be blogging here about everything I learn in my JavaScript classes from start to finish.

I hope that the information you find here will help you discover the strength of JavaScript, and how to be a better more efficient programmer.

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