18 JavaScript(Cont.)

8/6/2019 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



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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



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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));



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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)



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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";



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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");



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The Math object allows you to perform mathematical

tasks


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



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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()



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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



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Questions???


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