JavaScript

1
Chapter 19

• JavaScript

2
JavaScript

• Interpretive programming language
• Its designed to work inside web pages uses
  ltscriptgt tag
• Ex. ltscript languagejavascriptgt lt/scriptgt
• It can be embedded in anywhere in the XHTML code
• Nesting ltscriptgt tag generates a syntax error
• Case sensitive sum, Sum, SUM are different

3
JavaScript

• You need to know three major things to learn a
  programming language now
• Language Syntax/Rules
• Event handling
• Object Oriented Programming (OOP) concept

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JavaScript

• Language Syntax/Rules
• Variable symbolic name can store a value
• Identifiers begin with letter, underscore, or
  dollar sign
• Types number 30, 3.14, -25, -2.4
• Boolean true or false (reserved words)
• String 25 dollars, totalvalue
• Var sum 100
• Name tim
• Scope global V.S. local (Var statement)
• Constants const pi 3.14
• Special character \

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JavaScript

• Statements a line of JavaScript code
• Use sign -gt x 20 y x
• Must end with a -gt x y 20
• Must not be broken in to two lines.
• Comments // inline comments
• / block comments /

6
JavaScript

• Expressions Operators
• Assignment operators , , -, , /
• y 30 x x y x y
• Comparison operators , !, , !, gt, gt, lt,
  lt
• A (x y) B (z gt 20)
• Arithmetic operators , -, , /, , , - -, and
  (negative)
• x10 x x y5 y- - y
• Logical Operators (and), II (or), ! (not)
• (T F) (F T) (F F) (F F) (! T) False
  
• (T F) (F T) (T T) (T T) (! F) True
• x true yfalse z !( x y) z ?

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JavaScript

• Control Structures - Conditional (if and switch)
• if (condition) true block
• else false block
• switch (expression)
• case label1 statement break
• case label2 statement break
• default statement
• see example 19.5

8
JavaScript

• Control Structures loops
• Loops need a control value/counter to set the
  looping time
• for loop
• for (initial value of counter condition
  increment)
• looping statements
• for (counter0 counterlt10 counter)
• document.write (for loop
  counter ltbr/gt)
• How many time does this loop go?

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JavaScript

• Control Structures loops
• while loop
• while (condition) looping statements
• counter 0
• while (counter lt 10)
• document.write (while loop counter
  ltbr/gt)
• counter
• // How many time does this loop go?
• See example 19.6, 19.7

10
JavaScript

• Control Structures loops
• do while loop
• do looping statements while (condition)
• counter 0
• do
• document.write (do while counter
  ltbr/gt)
• counter
• while (counter lt 10)
• How many time does this loop go?

11
JavaScript

• Control Structures loops
• infinite loops loop does not have a control
  value/counter to set the looping time

12
JavaScript

• Window input and output method
• You should not put XHTML tags in output string
• Id prompt(string, initial value)
• get_prompt prompt(click yes, 7)
• Id comfirm(string)
• Answer comfirm(the number is x)
• alert (string)
• alert (the answer is x)
• document.write() // for web page output