slide môn học HDJ bài 8 the core language objects in javascript

The Core language Objects in
JavaScript
Session 8


A Recap
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Scripting Language – Scenarios Language
JavaScript’s Elements
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Core JavaScript Object
Client-Side JavaScript Object
Server-Side JavaScript Object

JavaScript’s Tokens
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Variables
Data Types
Operators (Arithmetic, Comparison, Logical, String, Evaluation)

Expression
Regular Expression
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A Recap
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Various message boxes
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Function
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Alert
Confirm
Prompt
Pre-defined functions
User-defined functions
Return statement

Display Information

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Objectives
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Work on Core Language Objects

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Use object Attributes and Methods

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Objects
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The properties (variables) that define the
object and the methods (functions) that work
on the data are included in the object

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For example, a car is an object. The
properties of the car are its make, model, and
color. They have some common methods like,
go (), brake(), reverse().
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Properties and Methods
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To access the properties of the object, we
must specify the object name and the
property:
objectName.propertyName

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To access the methods of an object, we must
specify the object name and the required
method:
objectName.method ()
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Example
function Car(model, type)
{
this.model = “Toyota”;
this.type = “for King Nothing”;

}

this.run = function()
{
document.write(“Brmm…”);
}

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Using objects
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When creating a Web page we can insert:
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Browser objects

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Built in script language objects (vary depending
on the scripting language used)

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HTML elements

We can also create our own objects for use
in the programs.
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Object Hierarchy
Browser Objects

Script Objects

HTML Elements
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The this statement
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The this statement is more of an internal
property.

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Its value indicates the current object. It can
have standard properties such as name,
length and value applied accordingly.

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The for . . . in statement
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The for . . in statement is used to cycle
through each property of an object or each
element of an array.

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The syntax is:
for (variable in object)
{ statements; }
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The with statement
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The with statement is used to execute a set
of statements that have a specified object as
the reference.

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The property is assigned to the object
specified in the with statement.

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The syntax is:
with (object) { statements; }

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New Operator
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The new operator is used to create a new
instance of an object type
The object type may be user-define or built-in
objectName = new objectType (param1
[,param2] ...[,paramN])
where,
objectName is the name of the new object instance.
ObjectType is a function that defined the type of the object. For
example, Array.
Param[1, 2, . . ] are the property values of the object.
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Eval function
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The eval function is used to evaluate a string
of code without reference to any specific
object.
The string can be a JavaScript expression,
statement, or a group of statements
The expression can include variables and
properties of an object.

var x = 5;
var z = 10;
document.write(eval(“x + z + 5”));
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String object
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The string object is used to manipulate and
work with strings of text.
We can extract substrings and convert text to
upper- or lowercase characters in a program.
The general syntax is,
stringName.propertyName

or
stringName.methodName
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Creating String object
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There are 3 different methods of creating
strings.

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Using the var statement

and optionally

assigning it to a value.
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Using an assignment operator (=) with a
variable name.

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Using the string () constructor.
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String Object
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Properties
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length

Methods
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charAt(index)
charCodeAt(index)
fromCharCode(icode, icode, icode…)
indexOf(findString, pos)
lastIndexOf(findString, pos)
Substring(start, end)
toLowerCase(), toUpperCase
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Math Object
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The Math object has properties and
methods that represent advanced
mathematical calculations.
function doCalc(x)
var a;
a = Math.PI * x
alert("The area
with a radius of "
a);
}

{
* x;
of a circle
+ x + “ is "

+

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Math Object
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Properties
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PI

Methods
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abs(number)

ceil(number)
floor(number)
round(number)
random()
pow(number, exp)
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Date object
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The Date built-in object contains both date
and time information.

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The

Date

object

does

not

have

any

properties.


It has a large number of methods for setting,
getting, and manipulating dates.
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Date object
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The Date object stores dates as the number
of

milliseconds

since

January

1,

1970,

00:00:00.
DateObject = new Date(parameters)

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Date Object
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Properties
Methods
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getDate()
getDay()
getMonth()
getFullYear()
getHours()
getMinutes
getSeconds
getMiliseconds

setDate()
setMonth()
setFullYear()

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Array Object
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Properties
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length

Methods
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concat()
slice(start, end)
join()
sort()
reverse()

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Timers
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One Shot Timer
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setTimeout(“javaScript code”, delay)

Timer that Fires at Regular Intervals
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setInterval(“javaScript code”, interval)
clearInterval(handler)

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