1. Chapter 19
JavaScript

2. JavaScript Interpretive programming language
It’s designed to work inside web pages uses <script> tag
Ex. <script language=“javascript”> </script>
It can be embedded in anywhere in the XHTML code
Nesting <script> 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

4. 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: \

5. JavaScript Statements: a line of JavaScript code
Use “=“ sign -> x = 20; y = x;
Must end with a “;” -> 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 == , !=, ===, !==, >, >=, <, <=
A = (x == y); B = (z >= 20);
Arithmetic operators +, -, *, /, %, ++, - -, and – (negative)
x=10; ++x; x++; y=5; 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; y=false; z = !( x && y); z = ?

7. 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 for loop:
Loops need a control value/counter to set the looping time
for loop:
for (initial value of counter; condition; increment)
{looping statements}
for (counter=0; counter<10; counter++)
{document.write (“for loop = “ + counter + “<br/>”);}
How many time does this loop go?

9. JavaScript Control Structures – loops while loop:
while (condition) {{looping statements}
counter = 0;
while (counter < 10)
{document.write (“while loop= “ + counter + “<br/>”);
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 + “<br/>”);
counter++;
} while (counter < 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 document.write() // for web page output
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