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Introduction to Computing

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Introduction to Computing ­ CS101
VU
Lesson 38
String Manipulations
(Web Development Lesson 13)
During the last Lesson we discussed Mathematical Methods
·
We looked at the properties and methods of JavaScript's Math object
·
We produced solutions for simple problems using several methods of the Math object
Problems & Solutions
·
JavaScript doesn't support drawing of graphics
·
However, crude graphics can be put together with the help of various text characters or tables
·
One cannot write a character at a random location on the screen using JavaScript
·
Instead, the graph has to be drawn from top to bottom, one row at a time ­ just like when regular
text is written to a document
Mathematical Functions in JavaScript
·
In addition to the simple arithmetic operations (e.g. +, *, etc.) JavaScript supports several advanced
mathematical operations as well
·
Notationaly, these functions are accessed by referring to various methods of the Math object
·
Moreover, this object also contains several useful mathematical constants as its properties
·
This object has no use, but of a placeholder
Properties
Math.PI
Note the
Math.E
CAPITAL
Math.LN2
lettering of
Math.LN10
all
Math.LOG2E
properties
Math.LOG10E
Math.SQRT2
Math.SQRT1_2
Methods
sin( r )
sqrt( x )
round( x )
cos( r )
pow( x, y )
floor( x )
tan( r )
ceil( x )
asin( x )
acos( x )
exp( x )
atan( x )
log( x )
atan2( x, y
abs( x )
)
max( x, y
)
random( )
max( x, y
)
sin( r ), cos( r ), tan( r )
Standard trigonometric functions
Returns the sine, cosine or tangent of `r',
where `r' is specified in radians
EXAMPLE
0.7071067811865476
document.write( Math.cos( Math.PI / 4 ) )
asin( x ), acos( x ), atan( x )
Standard inverse-trigonometric functions
Returns the arcsine, arccosine or arctangent of `r'
in radians
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EXAMPLE
document.write( Math.asin( 1 ) )
sqrt( x )
pow( x, y )
Returns the square root of x
Returns x raised to the power y
exp( x )
log( x )
0.5 0.7071
2, 32
4294967296
Returns Math.E raised to
Returns the the natural
logarithm of x
the power x
ceil( x )
1 2.718281
Math.E 1
round( x )
floor( x )
Returns integer
Returns largest integer
Returns smallest
nearest to x
that is less than or
integer that is greater
equal to x
than or equal to x
1.1 1
1.1 2
1.1 1
12.5 13
12.5 13
12.5 12
-13.9 -14
-13.9 -13
-13.9 -14
abs( x )
Returns the absolute value
of x
1.1 1.1
-12.5 12.5
00
min( x, y )
max( x, y )
Returns the smaller of x and y
Returns the larger of x and y
2, 4 4
2, 4 2
-12, -5 -5
-12, -5 -12
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Introduction to Computing ­ CS101
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random( )
Returns a randomly-selected, floating-point number between 0 and 1
EXAMPLE
document.write( Math.random( ) )
0.9601111965589273
random( ): Example
Design a Web page that displays the result of the rolling of a 6-sided die on user command
Today's Goal
(String Manipulation)
·
To become familiar with methods used
for manipulating strings
****
·
To become able to solve simple
problems involving strings
String Manipulation Examples
·
Combine these words into a sentence
i.e. take these strings and concatenate them into one
·
Break this string into smaller ones
·
Convert this string into upper case
·
See if a particular character exists in a string
·
Find the length of a string
·
Convert this string into a number
38.1 String Manipulation in JavaScript
·
In addition to the concatenation operator (+) JavaScript supports several advanced string
operations as well
·
Notationaly, these functions are accessed by referring to various methods of the String object
·
Moreover, this object also contains the `length' property
Example
name = "BHOLA" ;
document.write
( "The length of the
string `name' is ", name.length ) ;
Let us now revisit an example that we first
discussed in the 18th lecture
Let us see how we put the `length' property of
a string to good use
The length of the string `name' is 5
<HTML>
<HEAD>
<TITLE>Send an eMail</TITLE>
<SCRIPT>
function checkForm( ) { ... }
</SCRIPT>
</HEAD>
<BODY bgcolor="#FFFFCC">
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<TABLE><FORM ...>...</FORM></TABLE>
</BODY>
</HTML>
<TABLE>
...
<FORM ...>
<INPUT
type="submit"
name="sendEmail"
value="Send eMail"
onMouseOver="checkForm( )"
>
...
</FORM>
</TABLE>
This is a
string
function checkForm( ) {
if( document.sendEmail.sender.value.length < 1 ) {
window.alert(
"Empty From field! Please correct" ) ;
}
}
Other Uses of the `length' Property
·
To restrict the length of login name or password to specified bounds, i.e. no less than 4 and no
more than 8 characters
·
???
String Methods
FORMAT
string.methodName( )
EXAMPLE:
name = "Bhola" ;
BHOLABhola
document.write( name.toUpperCase( ) ) ;
document.write( name.bold( ) ) ;
Two Types of String Methods
1.HTML Shortcuts
2.All Others
String Methods: HTML Shortcuts
bold( )
big( )
italics( )
link( URL )
small( )
strike( )
fontsize( n )
sub( )
fixed( )
sup( )
fontcolor( color )
big( ), small( ), fontsize( n )
person = "Bhola" ;
BholaBholaBholaBholaBhola
document.write( person ) ;
document.write( person.big( ) ) ;
document.write( person.small( ) ) ;
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document.write( person.fontsize( 1 ) ) ;
document.write( person.fontsize( 7 ) ) ;
sub( ), sup( )
person = "Bhola" ;
document.write( name ) ;
document.write( name.sub( ) ) ;
document.write( name ) ; document.write( name.sup( ) ) ;
bold( ), italics( ), strike( )
name = "Bhola" ;
document.write( name ) ;
document.write( name.bold( ) ) ;
document.write( name.italics( ) ) ;
document.write( name.strike( 1 ) ) ;
fixed( ), fontcolor( color )
person = "Bhola" ;
document.write( person ) ;
document.write( person.fixed( ) ) ;
document.write( person.fontcolor( "blue" ) ) ;
document.write( person.fontcolor( "orange" ) ) ;
link( URL )
hotel = "Bhola Continental" ;
document.write( hotel ) ;
document.write( hotel.link(
"http://www.bholacontinental.com" ) ) ;
What was common among all those methods that we just discussed?
big( )
<BIG> ... </BIG>
<SMALL> ... </SMALL>
small( )
fontsize( n )
<FONT size=n> ...
</FO
sub( )
<SUB> ... </SUB>
NT>
sup( )
<SUP> ... </SUP>
fontcolor( color )
<FONT color=color>
...
bold( )
<B> ... </B>
fixed( )
<PRE> ... </PRE>
italics( )
<I> ... </I>
link( URL )
<A href=URL>
</A>
strike( )
<S> ... </S>
String Methods: All Others
toLowerCase( )
charAt( n )
toUpperCase( )
substring( n, m )
indexOf( substring, n )
lastIndexOf( substring, n )
split( delimiter )
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toLowerCase( ), toUpperCase( )
person = "Bhola" ;
BholabholaBHOLA
document.write( person ) ;
document.write( person.toLowerCase( ) ) ;
document.write( person.toUpperCase( ) ) ;
charAt( n )
Returns a string containing the character at position n (the position of the 1st character is 0)
mister = "Bhola" ;
document.write( mister ) ;
Bo
document.write( mister.charAt( 0 ) ) ;
document.write( mister.charAt( 8 ) ) ;
document.write( mister.charAt( 2 ) ) ;
substring( n, m )
Returns a string containing characters copied from positions n to m - 1
s = "Bhola" ;
document.write( s.substring( 1, 3 ) ) ;
hoBhola
document.write( s.substring( 0, s.length ) ) ;
indexOf( substring, n )
Returns the position of the first occurrence of substring that appears on or after the nth position, if any,
or -1 if none is found
s = "Bhola" ;
2-1
document.write( s.indexOf( "ola", 1 ) ) ;
document.write( s.indexOf( "z", 3 ) ) ;
lastIndexOf( substring, n )
Returns the position of the last occurrence of substring that appears on or before the nth position,
if any, or -1 if none is found
s = "Bhola" ;
document.write( s.lastIndexOf( "ola", 5 ) ) ;
2-1
document.write( s.lastIndexOf( "b", 0 ) ) ;
split( delimiter )
Returns an array of strings, created by splitting string into substrings, at delimiter boundaries
s = "Hello: I must be going!" ;
a = new Array( 5 ) ;
b = new Array( 5 ) ;
a = s.split( " " ) ;
b = s.split( "e" ) ;
document.write( "<TABLE>" ) ;
for( k = 0; k < 5; k = k + 1 )
document.write( "<TR><TD>", a[ k ], "</TD><TD>", b[ k ], "</TD></TR>" ) ;
document.write( "</TABLE>" ) ;
Hello:  H
I
llo: I must b
must
going!
be undefined
going!  undefined
Automatic Conversion to Strings
·
Whenever a non-string is used where JavaScript is expecting a string, it converts that non-string
into a string
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Introduction to Computing ­ CS101
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·
Example:
­  The document.write( ) method expects a string (or several strings, separated by commas) as its
argument
­  When a number or a Boolean is passed as an argument to this method, JavaScript automatically
converts it into a string before writing it onto the document
The `+' Operator
·
When `+' is used with numeric operands, it adds them
·
When it is used with string operands, it concatenates them
·
When one operand is a string, and the other is not, the non-string will first be converted to a string
and then the two strings will be concatenated
The `+' Operator: Examples
document.write( 2 + Math.PI ) ;
5.141592653589793
document.write( "2" + "3" ) ;
23
document.write( "2" + Math.PI ) ;
23.141592653589793
document.write( "Yes" + false ) ;
Yesfalse
Strings In Mathematical Expressions
When a string is used in a mathematical context, if appropriate, JavaScript first converts it into a
number. Otherwise, a "NaN" is the result
6.283185307179586
document.write( "2" * Math.PI ) ;
NaN
document.write( "Yes" ^ 43 ) ;
The `toString' Method
Explicit conversion to a string
100.55
EXAMPLE:
Convert 100.553478 into a currency format
a = 100.553478 ;
b = a.toString( ) ;
decimalPos = b.indexOf( ".", 0 ) ;
c = b.substring( 0, decimalPos + 3 ) ;
document.write( c ) ;
9
Conversion from Strings
parseInt( ) and parseFloat( ) methods
9
function calc( ) {
90
document.myForm.total.value =
document.myForm.salary.value +
document.myForm.bonus.value ;
}
function calc( ) {
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document.myForm.total.value =
Why not use
parseFloat( document.myForm.salary.value ) +
parseInt( ) here?
parseFloat( document.myForm.bonus.value ) ;
}
During Today's Lesson ...
·
We become familiar with methods used for manipulating strings
·
We became able to solve simple problems involving strings
Next (the 14th) Web Dev Lecture:
Images & Animation
·
To become able to add and manipulate images and animations to a Web page
263
Table of Contents:
  1. INTRODUCTION
  2. EVOLUTION OF COMPUTING
  3. World Wide Web, Web’s structure, genesis, its evolution
  4. Types of Computers, Components, Parts of Computers
  5. List of Parts of Computers
  6. Develop your Personal Web Page: HTML
  7. Microprocessor, Bus interface unit, Data & instruction cache memory, ALU
  8. Number systems, binary numbers, NOT, AND, OR and XOR logic operations
  9. structure of HTML tags, types of lists in web development
  10. COMPUTER SOFTWARE: Operating Systems, Device Drivers, Trialware
  11. Operating System: functions, components, types of operating systems
  12. Forms on Web pages, Components of Forms, building interactive Forms
  13. APPLICATION SOFTWARE: Scientific, engineering, graphics, Business, Productivity, Entertainment, Educational Software
  14. WORD PROCESSING: Common functions of word processors, desktop publishing
  15. Interactivity to Forms, JavaScript, server-side scripts
  16. ALGORITHMS
  17. ALGORITHMS: Pseudo code, Flowcharts
  18. JavaScript and client-side scripting, objects in JavaScript
  19. Low, High-Level, interpreted, compiled, structured & object-oriented programming languages
  20. Software Design and Development Methodologies
  21. DATA TYPES & OPERATORS
  22. SPREADSHEETS
  23. FLOW CONTROL & LOOPS
  24. DESIGN HEURISTICS. Rule of thumb learned through trial & error
  25. WEB DESIGN FOR USABILITY
  26. ARRAYS
  27. COMPUTER NETWORKS: types of networks, networking topologies and protocols
  28. THE INTERNET
  29. Variables: Local and Global Variables
  30. Internet Services: FTP, Telnet, Web, eMail, Instant messaging, VoIP
  31. DEVELOPING PRESENTATIONS: Effective Multimedia Presentations
  32. Event Handlers
  33. GRAPHICS & ANIMATION
  34. INTELLIGENT SYSTEMS: techniques for designing Artificial Intelligent Systems
  35. Mathematical Functions in JavaScript
  36. DATA MANAGEMENT
  37. DATABASE SOFTWARE: Data Security, Data Integrity, Integrity, Accessibility, DBMS
  38. String Manipulations:
  39. CYBER CRIME
  40. Social Implications of Computing
  41. IMAGES & ANIMATION
  42. THE COMPUTING PROFESSION
  43. THE FUTURE OF COMPUTING
  44. PROGRAMMING METHODOLOGY
  45. REVIEW & WRAP-UP of Introduction to Computing