CHAPTER 10 JAVA SCRIPT

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CHAPTER 10JAVA SCRIPT
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JAVA SCRIPT

• Language that will allow you to add real
  programming to your web pages.
• Most of the browser today have their JavaScript
  interpreter.
• We used JavaScript for
• Browser Detection-Detecting the browser used by a
  visitor at your page.
• Cookies- To store the information on the visitor
  computer and then retrieve this information
  automatic next time the user visit your page.
• Control Browsers- Opening pages in customized
  windows, where you specify if the browsers
  buttons, menu line, status line or whatever
  should be present.
• Validate Forms-Validating inputs to fields before
  submitting a form.

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HOW TO ADD JAVA SCRIPT

• This script tell the browser where JavaScript
  starts and ends.
• Syntax ltScript languageJavaScriptgt
  lt/Scriptgt
• Example
• ltHTMLgt
• ltBODYgt
• ltScript language JavaScriptgt
• //type the message/text
• lt/Scriptgt
• lt/BODYgt
• lt/HTMLgt

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IMPORTANT !

• A few things you need to know before you write a
  JavaScript code
• JavaScript-lines ends with a semicolon().
• Should always put the text within .
• If you forget to enclose your text in ,
  JavaScript will interpret your text as being
  variables rather than text.
• Capital letter are different from non-capital
  letters.(so you need to follow the capital
  letters at exactly the right places)

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VARIABLES

• All variables are referred to the unique name you
  assigned to them.
• The variable with capital letter is difference
  with variable non-capital letters.
• Example Myname , MyName.

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ASSIGN VALUE TO VARIABLE

• Used equal-sign.
• We can assign a value or text to variables.
• Example
• Assigned a text to variables
• FirstNameDit4
• Assigned a value to variables
• a 3 a
• Used a standard operator such as -, , and / in
  our web page.
• We also can used , -- and operator for
  increment, decrement and returns modulus value to
  a variable.
• Example
• a2 ba
• FirstNameAIM
• LastNameAlor Setar
• FullNameFirstName LastName

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MESSAGE BOX

• Three pop-up windows that we can add in our web
  pages.
• alertbox
• confirmbox
• promptbox

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ALERTBOX

• Used when we want to make sure an information
  comes through to the user.
• Syntax alert (text)
• Example
• alert(Welcome to my homepage)
• Message box windows will provide the OK button.
  
• So user need to click OK to proceed.

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COMFIRMBOX

• Used when we want the user to agree to or accept
  something.
• Syntax confirm (your text)
• Example confirm (You are 20 years old)
• Message box window will provide the OK and
  Cancel button, so user need to click OK button
  or CANCEL button to proceed.
• OK returns the value true
• CANCEL returns the value false.

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PROMPBOX

• Used when the user should input a value before
  entering the page.
• Example enter username, password.
• Used together with variables.
• Syntax
• prompt (your text, default value)
• Example
• Username prompt(please enter your name,
  enter your name here)
• User need to click OK button or CANCEL
  button after entering the text.
• OK the promptbox returns the entry.
• CANCEL the promptbox returns null.

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SELECTION

• The selection control structure in JavaScript
  are
• If selection
• If/else selection
• Nested if selection
• Multiple selection (switch)
• Comparing operator
• equal to
• ! not equal to
• lt less than
• gt greater than
• lt less than or equal to
• gt greater than or equal to

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IF SELECTION

• Syntax
• if (condition)action 1
• Example
• if (browser Mozila Firefox)
• alert (you are using Mozila Firefox)

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IF/ELSE SELECTION

• Syntax
• if (condition)action 1
• else action 2
• Example
• if (browser Mozila Firefox)
• alert (you are using Mozila Firefox)
• else
• alert (you are using Netscape)

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NESTED IF

• Example
• a prompt(please enter first number, 0)
• b prompt (please enter second number,
  0)
•   if (ab)
• if (agt0)
• Alert (both number are equal and a is
  positive number)

• Syntax
• if (condition)
• if (condition)
• action 2
• else
• action 3

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MULTIPLE SELECTION (SWITCH)

• Is used to handle decision making.
• Syntax
• switch (variablename)
• case label_1 statements_1 break
• case label_2 statements_2 break
• case label_n statement_n break
• default statements

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BOOLEAN OPERATOR

• We call as a logical operator and use to enhance
  our if statement.
• Example of logical operator AND (), OR ()
  and NOT (!).
• AND - Use when we want to check if more than one
  condition to be true.
• OR- Use when we want to check if more than one
  condition should result in the check
  being true.
• NOT- Use to invert whatever we are checking for.

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LOOP

• Used to make sure we can display data for more
  then one times.
• 3 different loop
• for loop
• while loop
• do while loop

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FOR LOOP WHILE LOOP

• FOR LOOP
• Used when we know in advance how many times the
  script should perform the similar task.
• Syntax
• for (variablestartvalue variableltendvalue
  variable variable incrementfactot)
• WHILE LOOP
• Used when we dont know in advance how many times
  the loop should be performed.
• Syntax
• while (variable ltendvalue)
• //type the JavaScript code,increment and
  decrement

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DO WHILE LOOP

• Used when we dont know in advance how many times
  the loop should be performed.
• Same with while loop, but in do.. While its test
  the condition at the end of the loop body.
• The loop body always executed at least once.
•  
• Syntax
• do
• //type the JavaScript code
• Increment/ decrement
• while (variable ltendvalue)

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FUNCTION

• The best way to develop and maintain a large
  program is to construct it small, simple pieces
  or modules.
• Modules in JavaScript are called functions.
• JavaScript programs are written by combining new
  functions that the programmer writes with
  prepackaged functions and object available in
  JavaScript.
• The prepackaged functions that belong to
  JavaScript objects (such as Math.pow and
  Math.round) are often called methods.

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• JavaScript provides several objects that have a
  rich collection of methods for performing common
  mathematical calculations, string manipulations,
  date and time manipulations and manipulations of
  collections of data called Arrays.
• The programmer can write functions to define
  specific tasks that may be used at many points in
  a script (referred as a programmer-defined
  functions).
• A function is invoked by a function call.
• The function call specifies the function name and
  provides information (as arguments) that the
  called function needs to do its task.

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USER DEFINED FUNCTION

• Syntax
• function functionname (variable1,variable2.)
• //here goes the Javascript for the function
• Must be type after ltscript Languagegt
• Must be spelled exactly as function.
• To call the function, just called the
  functionname that you give for your function.
•  

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ARRAY

• An array is a group of memory location that all
  have same name and same type.
• Array is used to help us to automate the process.
  
• When using variable-array, we need to define the
  array before referring it to any of the variable.
• 2 types of array
• One Dimension
• Two Dimension

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ONE DIMENSIONAL ARRAY

• Syntax
• Variablenamenew Array
• Example Assign data to array by using looping
• var valuenew Array
• for (number1 numberlt100 number number 1)
• valuenumber number 10