18 JavaScript(Cont.)
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Transcript of 18 JavaScript(Cont.)
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Resource Person: Muhammad Babar Nazir
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JavaScript Objects String Object
Date Object
Array Object Boolean Object
Math Object
RegExp Object
Browser Detection
Form Validation
E-mail Validation 2
Resource Person: Muhammad Babar Nazir
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JavaScript is an Object Oriented Programming
(OOP) language
There are many built-in objects available inJavaScript
We will explore some important object in
JavaScript
Resource Person: Muhammad Babar Nazir
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The String object is used to manipulate a
stored piece of text
There are many methods available tomanipulate strings
var txt="Hello world!";
document.write(txt.length);
document.write(txt.toUpperCase());
document.write(txt.indexOf(w));
Resource Person: Muhammad Babar Nazir
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The Date object is used to work with dates and
times
There are four types of constructors available toinstantiate Date object
new Date() // current date and time
new Date(milliseconds) //since 1970/01/01
new Date(dateString)new Date(year, month, day, hours, minutes,
seconds, milliseconds)
Resource Person: Muhammad Babar Nazir
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The Array object is used to store multiple values
in a single variable
An array is a special variable, which can holdmore than one value, at a time
var myCars=new Array();
myCars[0]="Saab";
myCars[1]="Volvo";
myCars[2]="BMW";
Resource Person: Muhammad Babar Nazir
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Three ways to initialize an array
var myCars=new Array();
var myCars=new Array("Saab","Volvo","BMW");
var myCars=["Saab","Volvo","BMW"];
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The Boolean object is used to convert a non-Boolean value to a Boolean value (true or false)
To construct an object with false value
var myBoolean=new Boolean();var myBoolean=new Boolean(0);var myBoolean=new Boolean(null);var myBoolean=new Boolean("");
var myBoolean=new Boolean(false);var myBoolean=new Boolean(NaN);
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To construct an object with true value
var myBoolean=new Boolean(true);
var myBoolean=new Boolean("true");
var myBoolean=new Boolean("false");
var myBoolean=new Boolean("Richard");
Resource Person: Muhammad Babar Nazir
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The Math object allows you to perform mathematical
tasks
Resource Person: Muhammad Babar Nazir
abs(x) Returns the absolute value of x
acos(x) Returns the arccosine of x, in radians
asin(x) Returns the arcsine of x, in radians
atan(x) Returns the arctangent of x as a numeric value between -PI/2 and PI/2 radians
atan2(y,) Returns the arctangent of the quotient of its arguments
ceil(x) Returns x, rounded upwards to the nearest integer
cos(x) Returns the cosine of x (x is in radians)
exp(x) Returns the value of Ex
floor(x) Returns x, rounded downwards to the nearest integer
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log(x) Returns the natural logarithm (base E) of x
max(x,y,z,...,
n)Returns the number with the highest value
min(x,y,z,...,
n)Returns the number with the lowest value
pow(x,y) Returns the value of x to the power of y
random() Returns a random number between 0 and 1
round(x) Rounds x to the nearest integer
sin(x) Returns the sine of x (x is in radians)
sqrt(x) Returns the square root of x
tan(x) Returns the tangent of an angle
Resource Person: Muhammad Babar Nazir
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A regular expression is an object that describesa pattern of characters
Regular expressions are used to perform
pattern-matching and "search-and-replace"functions on text
var patt1=new RegExp("e");
The RegExp Object has 3 methods: test()
exec()
compile()
Resource Person: Muhammad Babar Nazir
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The Navigator object contains information about the visitor'sbrowser
var browser=navigator.appName;var b_version=navigator.appVersion;var version=parseFloat(b_version);
document.write("Browser name: "+ browser);document.write("
");document.write("Browser version: "+ version);
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function detectBrowser()
{var browser=navigator.appName;
var b_version=navigator.appVersion;
var version=parseFloat(b_version);
if ((browser=="Netscape"||browser=="Microsoft Internet Explorer")
&& (version>=4))
{alert("Your browser is good enough!");
}
else
{
alert("It's time to upgrade your browser!");
}
}
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JavaScript can be used to validate data inHTML forms before sending off the content to aserver
Form data that typically are checked by aJavaScript could be
has the user left required fields empty?
has the user entered a valid e-mail address? has the user entered a valid date?
has the user entered text in a numeric field?
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function validate_required(field,alerttxt){if (value==null||value=="")
{alert(alerttxt);return false;
}else
{return true;}
}
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function validate_email(field,alerttxt){with (field){apos=value.indexOf("@");dotpos=value.lastIndexOf(".");if (apos
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JavaScript Popup Boxes
JavaScript Functions
JavaScript Events
Resource Person: Muhammad Babar Nazir
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Questions???
Resource Person: Muhammad Babar Nazir