UNIT 5 FUNCTIONS, OBJECTS, CONDITIONS, AND LOOPS.
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UNIT 5
FUNCTIO
NS,
OB JE
CTS ,
CON
DIT
ION
S, AN
D L
OO
PS
OBJECTIVES CO6 Create a dynamic website using
JavaScript.
2
LEARNING OUTCOMESLO25 Create a JavaScript function.
LO26 Create custom objects.
LO27 Use and extend built-in objects.
LO28 Write code that uses conditional statements.
LO29 Write code that uses loops.
3
FUNCTION DEFINITION
function Greet() {
alert("Greetings.");
}
4
FUNCTION WITH PARAMETERS
function Greet(who){
alert("Greetings," + who);
}
5
FUNCTION IN A <HEAD><!DOCTYPE html ><head><title>Functions</title><script type="text/javascript">function Greet(who){alert("Greetings," + who);
}</script></head></html>
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CALLING THE FUNCTION
<body><h1>Function Example</h1><p>Prepare to be greeted twice.</p><script type="text/javascript">Greet("Fred");Greet("Ethel");</script></body>
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GREET FUNCTION OUTPUT
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A FUNCTION THAT RETURNS A VALUE<head><title>Function Example: Average</title><script type="text/javascript">function Average(a,b,c,d){result = (a + b + c + d)/4;return result;
}</script></head>
9
CALLING THE AVERAGE FUNCTION<body><h1>Function Example: Average</h1><p>The following is the result of the function call.</p>
<script type="text/javascript">score = Average(3,4,5,6);document.write("The average is:" + score);
</script></body>
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TYPES OF OBJECTS
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Built-in objects
DOM objects
Custom objects
CREATING OBJECTS
scores = new Array(4);
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PROPERTIES A variable stored within the object
test = "This is a test.";document.write(test.length);
Each property has a valuelocation.href=
"http://www.google.com/";
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METHOD
Function that works with the object's data
location.reload();
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USING CUSTOM OBJECTS Name the object
Identify its properties
Create a constructor
Define object methods
Create an instance of an object
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OBJECT CONSTRUCTORfunction Card(name,address,work,home) {
this.name = name;
this.address = address;
this.workphone = work;
this.homephone = home;
}
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DEFINING METHODS Write a function
Add the function definition to the constructor
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WRITE A FUNCTIONfunction PrintCard() {line1 = "Name: " + this.name + "<br/>\n";line2 = "Address: " + this.address + "<br/>\n";
line3 = "Work Phone: " + this.workphone + "<br/>\n";
line4 = "Home Phone: " + this.homephone + "<hr/>\n";
document.write(line1, line2, line3, line4);
}
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ADD THE FUNCTION DEFINITION TO THE CONSTRUCTORfunction Card(name,address,work,home) {
this.name = name;this.address = address;this.workphone = work;this.homephone = home;this.PrintCard = PrintCard;}
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CREATING AN OBJECT INSTANCE
tom = new Card("Tom Jones",
"123 Elm Street", "555-1234", "555-9876");
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ASSIGN PROPERTY VALUES AFTER OBJECT CREATION
holmes = new Card();
holmes.name = "Sherlock Holmes";
holmes.address = "221B Baker Street";
holmes.workphone = "555-2345";
holmes.homephone = "555-3456";
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EXTENDING BUILT-IN OBJECTS
Use the prototype keyword to add a property or method to a built-in object.
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ADDING A METHOD TO THE STRING OBJECT<script type="text/javascript">function addhead (level) {html = "h" + level;text = this.toString();start = "<" + html + ">";stop = "</" + html + ">";return start + text + stop;}String.prototype.heading = addhead;document.write ("This is a heading 1".heading(1));document.write ("This is a heading 2".heading(2));document.write ("This is a heading 3".heading(3));</script>
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MATH OBJECT Math.ceil() rounds a number up to the
next integer.
Math.floor() rounds a number down to the next integer.
Math.round() rounds a number to the nearest integer.
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ROUNDING EXAMPLE
function round(num) {
return Math.round(num * 100) / 100;
}
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GENERATING RANDOM NUMBERSfunction rand(num) {
return Math.floor(Math.random() * num) + 1;
}
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WITH KEYWORD
with (lastname) {
window.alert("length of last name: " + length);
capname = toUpperCase();
}
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DATE FORMATS
birthday = new Date();
birthday = new Date
("November 1, 2010 08:00:00");
birthday = new Date(11,1, 2010);
birthday = new Date(11,1,2010, 8, 0, 0);
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DATE OBJECT SET METHODS setDate()
setMonth()
setFullYear()
setTime()
setHours()
setMinutes
setSeconds()
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getDate()
getMonth()
getFullYear()
getTime()
getHours()
getMinutes()
getSeconds()
getMilliseconds()
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DATE OBJECT GET METHODS
getTimeZoneOffset()
toUTCString()
toLocalString()
getUTCDate()
getUTCDay()
getUTCFullYear()
getUTCMonth()
getUTCHours()
getUTCMinutes()
getUTCSeconds()
getUTCMilliseconds()
setUTCDate()
setUTCFullYear()
setUTCMonth()
setUTCHours()
setUTCMinutes()
setUTCSeconds()
setUTCMilliseconds()
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WORKING WITH TIME ZONES
CONVERTING BETWEEN DATE FORMATS Date.parse()method converts a date
string, such as November 1, 2010, to a Date object (number of milliseconds since 1/1/1970).
Date.UTC() method does the opposite. It converts a Date object value (number of milliseconds) to a UTC (GMT) time.
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IF STATEMENT
if (a == 1) window.alert("Found a 1!");
if (a == 1) {
window.alert("Found a 1!");
a = 0;
}
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CONDITIONAL OPERATORS
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Operator Meaning== Is equal to!= Is not equal to< Is less than> Is greater than
>= Is greater than or equal to<= Is less than or equal to
LOGICAL OPERATORS Or
if ((phone == "") || (email == "")) window.alert("Something’s Missing!");
Andif ((phone == "") && (email == "")) window.alert("Both are Missing!");
Notif (!(phone == "")) alert("phone is OK");
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THE ELSE KEYWORD
if (a == 1) {
alert("Found a 1!");
a = 0;
} else {
alert("Incorrect value: " + a);
}
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SHORTHAND CONDITIONAL EXPRESSIONSvalue = (a == 1) ? 1 : 0;
Same asif (a == 1) {
value = 1;
} else {
value = 0;
}
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SHORTHAND EXAMPLE
document.write("Found " + counter +
((counter == 1) ? " word." : " words."));
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TESTING MULTIPLE CONDITIONSWITH IF AND ELSEif (hours < 10) {document.write("Good morning.");} else if (hours >= 14 && hours <= 17) {document.write("Good afternoon.");} else if (hours >= 17) {document.write("Good evening.");} else {document.write("Good day.");}
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TESTING MULTIPLE CONDITIONS WITH SWITCHswitch(button) {
case "next":window.location="next.html";
break;case "previous":
window.location="prev.html";break;case "home":
window.location="home.html";break;case "back":
window.location="menu.html";break;default:
window.alert("Wrong button.");} 40
FOR LOOPfor (i=0; i<10; i++) {
document.write("This is line " + i + "<br />");
}
for (i=0; i<10; i++)
document.write("This is line " + i + "<br />");
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WHILE LOOP
while (total < 10) {
n++;
total += values[n];
}
for (n=0; total < 10; n++) {
total += values[n];
}
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DO...WHILE LOOPS
do {
n++;
total += values[n];
}
while (total < 10);
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INFINITE LOOP A loop that never reaches the exit
condition
while (i < 10) {n++;values[n] = 0;
}
Can make the browser stop responding
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BREAK STATEMENT
while (true) {
n++;
if (values[n] == 1) break;
}
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CONTINUE STATEMENT
for (i=1; i<21; i++) {
if (score[i]==0) continue;
document.write(
"Student number ",i,
" Score: ", score[i],
"\n");
}
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LOOPING THROUGH OBJECT PROPERTIES
for (i in navigator) {
document.write("property: " + i);
document.write(" value: " + navigator[i] + "<br>");
}
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