JavaScript Lecture 4

1
JavaScript Lecture 4

• Assignment
• Review (examples for- if, prompts)
• Functions
• Note The following slides give the code and the
  output of the examples covered in class.

2
lthtmlgt ltheadgt lttitlegtIFlt/titlegt lt/headgt ltbody
gt ltscript type "text/javascript"gt var
watertemp0 var waterstate"liquid"
var description"water" if (watertemp lt
0) waterstate "frozen"
description "ice" document
.write("ltbrgtltbrgt") document.write("Watertemp
"watertemp"ltbrgt") document.write
("Waterstate "waterstate"ltbrgt")
document.write ("Description
"description) lt/scriptgt lt/bodygt lt/htmlgt
3
OUTPUT

• Watertemp 0
• Waterstate frozen
• Description ice
• Note change the value for watertemp and check
  the output

4

• lthtmlgt
• ltheadgt lttitlegtSIMPLE IFlt/titlegtlt/headgt
• ltbodygt
• ltscript type "text/javascript"gt
• var a true
• if (atrue)
• document.write("true")
• if (afalse)
• document.write("false")
• lt/scriptgt
• lt/bodygt
• lt/htmlgt

5
OUTPUT

• true

6

• lthtmlgt
• ltheadgt lttitlegtSIMPLE IFlt/titlegtlt/headgt
• ltbodygt
• ltscript type "text/javascript"gt
• var a true
• if (a)
• document.write("true")
• if (!a)
• document.write("false")
• lt/scriptgt
• lt/bodygt
• lt/htmlgt

7
OUTPUT

• true
• Note The last two programs are equivalent and
  give the same output.

8

• lthtmlgt
• ltheadgt lttitlegtSIMPLE IFlt/titlegtlt/headgt
• ltbodygt
• ltscript type "text/javascript"gt
• var a 3
• if (a)
• document.write("true")
• if (!a)
• document.write("false")
• lt/scriptgt
• lt/bodygt
• lt/htmlgt

9
OUTPUT

• true
• Note Change the value of a to 0 and see what
  happens.

10

• lthtmlgt
• ltheadgt
• lttitlegtCONFIRM IFlt/titlegt
• lt/headgt
• ltbodygt
• ltscript type "text/javascript"gt
• var a
• a confirm("Do you want to continue?")
• if (a)
• alert("You chose to continue")
• else
• alert("You chose to NOT continue")

11
Output Confirm box
12
Output after clicking on OK
13
Output after clicking on Cancel
14

• lthtmlgt
• ltheadgt lttitlegtIF ELSElt/titlegtlt/headgt
• ltbodygt
• ltscript type"text/javascript"gt
• var watertemp 5
• var waterstate
• var description
• if (watertemp lt0)
• waterstate "frozen"
• description "ice"
• else
• waterstate "liquid"
• description "water"

15
Output

• Watertemp 5
• Waterstate liquid
• Description water

16
Function Packages for algorithms

• Name
• Parameters
• Definition
• Also known as,
• procedures, subroutine, method etc

17

• function name (parameter list)
• statement list

18

• function print ()
• document.write(hello)