Lecture no 9.ppt operating system semester four
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About This Presentation
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Slide Content
Outline
IS400: Development of Business Applications on the Internet
Fall 2004
Instructor: Dr. Boris Jukic
JavaScript: Arrays
IS400: Development of Business Applications on the Internet
Fall 2004
Instructor: Dr. Boris Jukic
JavaScript: Arrays
Introduction
Arrays
–Data structures of related items
Each element has a position number
–Dynamic
Size of an array in JavaScript can be changed
(increased) AFTER it is created
Arrays
–Data structures of related items
Each element has a position number
–Dynamic
Size of an array in JavaScript can be changed
(increased) AFTER it is created
Arrays
Arrays in JavaScript
–Each element referenced by a number
Start at “zeroth element”: 10 element array has elements:
0,1,2 ,..,8,9
Subscript or index
–Accessing a specific element
Name of array
Brackets
Number of element
–Arrays know their length
lengthproperty
Arrays in JavaScript
–Each element referenced by a number
Start at “zeroth element”: 10 element array has elements:
0,1,2 ,..,8,9
Subscript or index
–Accessing a specific element
Name of array
Brackets
Number of element
–Arrays know their length
lengthproperty
c[ 6 ]
-45
6
0
72
1543
-89
0
62
-3
1
6453
78
Name of array
c[ 0 ]
c[ 1 ]
c[ 2 ]
c[ 3 ]
c[ 11 ]
c[ 10 ]
c[ 9 ]
c[ 8 ]
c[ 7 ]
c[ 5 ]
c[ 4 ]
Position number (index
or subscript) of the
element within array c
Fig. 11.1A 12-element array.
-45
6
0
72
1543
-89
0
62
-3
1
6453
78
Name of array
c[ 0 ]
c[ 1 ]
c[ 2 ]
c[ 3 ]
c[ 11 ]
c[ 10 ]
c[ 9 ]
c[ 8 ]
c[ 7 ]
c[ 5 ]
c[ 4 ]
Position number (index
or subscript) of the
element within array c
Fig. 11.1A 12-element array.
Declaring and Allocating Arrays
Arrays in memory
–Objects
–Operator new
Allocates memory for objects
Dynamic memory allocation operator
varc; array declaration
c = newArray( 12); memory allocation
Arrays in memory
–Objects
–Operator new
Allocates memory for objects
Dynamic memory allocation operator
varc; array declaration
c = newArray( 12); memory allocation
Using Arrays
Arrays can grow dynamically
–Allocate more space as more items are added
than originally planned for
Array elements must be initialized explicitly
–Default value is “undefined”
–forloops convenient fro initialization
–Referring to uninitialized elements or elements
outside array bounds is an error
Arrays can grow dynamically
–Allocate more space as more items are added
than originally planned for
Array elements must be initialized explicitly
–Default value is “undefined”
–forloops convenient fro initialization
–Referring to uninitialized elements or elements
outside array bounds is an error
Outline1 <?xml version = "1.0"?>
2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1 -strict.dtd">
4
5 <!-- Fig. 11.3: InitArray.html -->
6 <!-- Initializing an Array -->
7
8 <html xmlns = "http://www.w3.org/1999/xhtml" >
9 <head>
10 <title>Initializing an Array </title>
11
12 <script type = "text/javascript">
13 <!--
14 // this function is called when the <body> element's
15 // onload event occurs
16 function initializeArrays()
17 {
18 var n1 = new Array( 5 ); // allocate 5-element Array
19 var n2 = new Array(); // allocate empty Array
20
21 // assign values to each element of Array n1
22 for ( var i = 0; i < n1.length; ++i )
23 n1[ i ] = i;
Arrayn1has five elements.
The forloop initializes the elements in n1to
their subscript numbers (0 to 4).
Arrayn2is an empty array.
2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1 -strict.dtd">
4
5 <!-- Fig. 11.3: InitArray.html -->
6 <!-- Initializing an Array -->
7
8 <html xmlns = "http://www.w3.org/1999/xhtml" >
9 <head>
10 <title>Initializing an Array </title>
11
12 <script type = "text/javascript">
13 <!--
14 // this function is called when the <body> element's
15 // onload event occurs
16 function initializeArrays()
17 {
18 var n1 = new Array( 5 ); // allocate 5-element Array
19 var n2 = new Array(); // allocate empty Array
20
21 // assign values to each element of Array n1
22 for ( var i = 0; i < n1.length; ++i )
23 n1[ i ] = i;
Arrayn1has five elements.
The forloop initializes the elements in n1to
their subscript numbers (0 to 4).
Arrayn2is an empty array.
Outline24
25 // create and initialize five -elements in Array n2
26 for ( i = 0; i < 5; ++i )
27 n2[ i ] = i;
28
29 outputArray( "Array n1 contains", n1 );
30 outputArray( "Array n2 contains", n2 );
31 }
32
33 // output "header" followed by a two -column table
34 // containing subscripts and elements of "theArray"
35 function outputArray( header, theArray )
36 {
37 document.writeln( "<h2>" + header + "</h2>" );
38 document.writeln( "<table border = \"1\" width =" +
39 "\"100%\">" );
40
41 document.writeln( "<thead><th width = \"100\"" +
42 "align = \"left\">Subscript</th>" +
43 "<th align = \"left\">Value</th></thead><tbody>" );
The forloop adds five elements to Arrayn2and
initialize each element to its subscript number (0 to 4).
Each function displays the
contents of its respective Array
in an XHTML table.
The first time function ouputArrayis called,
variable headergets the value of “Array n1
contains”and variable theArraygets the
value of n1.
The second time function ouputArrayis
called, variable headergets the value of
“Array n2 contains”and variable
theArraygets the value of n2.
25 // create and initialize five -elements in Array n2
26 for ( i = 0; i < 5; ++i )
27 n2[ i ] = i;
28
29 outputArray( "Array n1 contains", n1 );
30 outputArray( "Array n2 contains", n2 );
31 }
32
33 // output "header" followed by a two -column table
34 // containing subscripts and elements of "theArray"
35 function outputArray( header, theArray )
36 {
37 document.writeln( "<h2>" + header + "</h2>" );
38 document.writeln( "<table border = \"1\" width =" +
39 "\"100%\">" );
40
41 document.writeln( "<thead><th width = \"100\"" +
42 "align = \"left\">Subscript</th>" +
43 "<th align = \"left\">Value</th></thead><tbody>" );
The forloop adds five elements to Arrayn2and
initialize each element to its subscript number (0 to 4).
Each function displays the
contents of its respective Array
in an XHTML table.
The first time function ouputArrayis called,
variable headergets the value of “Array n1
contains”and variable theArraygets the
value of n1.
The second time function ouputArrayis
called, variable headergets the value of
“Array n2 contains”and variable
theArraygets the value of n2.
Outline44
45 for ( var i = 0; i < theArray.length; i++ )
46 document.writeln( "<tr><td>" + i + "</td><td>" +
47 theArray[ i ] + "</td></tr>" );
48
49 document.writeln( "</tbody></table>" );
50 }
51 // -->
52 </script>
53
54 </head><body onload = "initializeArrays()" ></body>
55 </html>
45 for ( var i = 0; i < theArray.length; i++ )
46 document.writeln( "<tr><td>" + i + "</td><td>" +
47 theArray[ i ] + "</td></tr>" );
48
49 document.writeln( "</tbody></table>" );
50 }
51 // -->
52 </script>
53
54 </head><body onload = "initializeArrays()" ></body>
55 </html>
Examples Using Arrays
Examples Using Arrays
for…instatement
–Perform an action for each element in an array
–Iterates over array elements
Assigns each element to specified variable one at a time
–Ignores non-existent elements
for…instatement
–Perform an action for each element in an array
–Iterates over array elements
Assigns each element to specified variable one at a time
–Ignores non-existent elements
Outline
SumArray.html
(1 of 2)1 <?xml version = "1.0"?>
2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1 -strict.dtd">
4
5 <!-- Fig. 11.5: SumArray.html -->
6 <!-- Summing Elements of an Array -->
7
8 <html xmlns = "http://www.w3.org/1999/xhtml" >
9 <head>
10 <title>Sum the Elements of an Array </title>
11
12 <script type = "text/javascript">
13 <!--
14 function start()
15 {
16 var theArray = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ];
17 var total1 = 0, total2 = 0;
18
19 for ( var i = 0; i < theArray.length; i++ )
20 total1 += theArray[ i ];
21
22 document.writeln( "Total using subscripts: " + total1 );
23
The forloop sums the values contained in the 10-
element integer array called theArray.
SumArray.html
(1 of 2)1 <?xml version = "1.0"?>
2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1 -strict.dtd">
4
5 <!-- Fig. 11.5: SumArray.html -->
6 <!-- Summing Elements of an Array -->
7
8 <html xmlns = "http://www.w3.org/1999/xhtml" >
9 <head>
10 <title>Sum the Elements of an Array </title>
11
12 <script type = "text/javascript">
13 <!--
14 function start()
15 {
16 var theArray = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ];
17 var total1 = 0, total2 = 0;
18
19 for ( var i = 0; i < theArray.length; i++ )
20 total1 += theArray[ i ];
21
22 document.writeln( "Total using subscripts: " + total1 );
23
The forloop sums the values contained in the 10-
element integer array called theArray.
Outline
SumArray.html
(2 of 2)24 for ( var element in theArray )
25 total2 += theArray[ element ];
26
27 document.writeln( "<br />Total using for...in: " +
28 total2 );
29 }
30 // -->
31 </script>
32
33 </head><body onload = "start()"></body>
34 </html>
Variable elementis assigned a subscript
in the range of 0 up to, but not including,
theArray.length.
SumArray.html
(2 of 2)24 for ( var element in theArray )
25 total2 += theArray[ element ];
26
27 document.writeln( "<br />Total using for...in: " +
28 total2 );
29 }
30 // -->
31 </script>
32
33 </head><body onload = "start()"></body>
34 </html>
Variable elementis assigned a subscript
in the range of 0 up to, but not including,
theArray.length.
Multidimensional Arrays
Two-dimensional arrays analogous to tables
–Rows and columns
Specify row first, then column
–Two subscripts
Two-dimensional arrays analogous to tables
–Rows and columns
Specify row first, then column
–Two subscripts
Multidimensional Arrays
a[ 1 ][ 0 ]a[ 1 ][ 1 ]a[ 1 ][ 2 ]a[ 1 ][ 3 ]
Row 0
Row 1
Row 2
Column 0 Column 1 Column 2 Column 3
Row subscript (or index)
Array name
Column subscript (or index)
a[ 0 ][ 0 ]a[ 0 ][ 1 ]a[ 0 ][ 2 ]a[ 0 ][ 3 ]
a[ 2 ][ 0 ]a[ 2 ][ 1 ]a[ 2 ][ 2 ]a[ 2 ][ 3 ]
Two-dimensional array with three rows and four columns.
a[ 1 ][ 0 ]a[ 1 ][ 1 ]a[ 1 ][ 2 ]a[ 1 ][ 3 ]
Row 0
Row 1
Row 2
Column 0 Column 1 Column 2 Column 3
Row subscript (or index)
Array name
Column subscript (or index)
a[ 0 ][ 0 ]a[ 0 ][ 1 ]a[ 0 ][ 2 ]a[ 0 ][ 3 ]
a[ 2 ][ 0 ]a[ 2 ][ 1 ]a[ 2 ][ 2 ]a[ 2 ][ 3 ]
Two-dimensional array with three rows and four columns.
Multidimensional Arrays
Declaring and initializing multidimensional
arrays
–Group by row in square brackets
–Treated as arrays of arrays
–Creating array bwith one row of two elements
and a second row of three elements:
varb = [ [ 1, 2], [ 3, 4, 5] ];
Declaring and initializing multidimensional
arrays
–Group by row in square brackets
–Treated as arrays of arrays
–Creating array bwith one row of two elements
and a second row of three elements:
varb = [ [ 1, 2], [ 3, 4, 5] ];
Multidimensional Arrays
Also possible to use newoperator
–Create array bwith two rows, first with five
columns and second with three:
varb;
b = newArray( 2);
b[ 0] = newArray( 5);
b[ 1] = newArray( 3);
Also possible to use newoperator
–Create array bwith two rows, first with five
columns and second with three:
varb;
b = newArray( 2);
b[ 0] = newArray( 5);
b[ 1] = newArray( 3);
Outline
InitArray3.html
(1 of 2)1 <?xml version = "1.0"?>
2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1 -strict.dtd">
4
5 <!-- Fig. 11.13: InitArray3.html -->
6 <!-- Initializing Multidimensional Ar rays -->
7
8 <html xmlns = "http://www.w3.org/1999/xhtml" >
9 <head>
10 <title>Initializing Multidimensional Arrays </title>
11
12 <script type = "text/javascript">
13 <!--
14 function start()
15 {
16 var array1 = [ [ 1, 2, 3 ], // first row
17 [ 4, 5, 6 ] ]; // second row
18 var array2 = [ [ 1, 2 ], // first row
19 [ 3 ], // second row
20 [ 4, 5, 6 ] ]; // third row
21
22 outputArray( "Values in array1 by row" , array1 );
23 outputArray( "Values in array2 by row" , array2 );
24 }
Arrayarray1provides six initializers in
two rows.
Arrayarray2provides six initializers in
three rows.
Function outputArraydisplays each array’s
elements in a Web page.
InitArray3.html
(1 of 2)1 <?xml version = "1.0"?>
2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
3 "http://www.w3.org/TR/xhtml1/DTD/xhtml1 -strict.dtd">
4
5 <!-- Fig. 11.13: InitArray3.html -->
6 <!-- Initializing Multidimensional Ar rays -->
7
8 <html xmlns = "http://www.w3.org/1999/xhtml" >
9 <head>
10 <title>Initializing Multidimensional Arrays </title>
11
12 <script type = "text/javascript">
13 <!--
14 function start()
15 {
16 var array1 = [ [ 1, 2, 3 ], // first row
17 [ 4, 5, 6 ] ]; // second row
18 var array2 = [ [ 1, 2 ], // first row
19 [ 3 ], // second row
20 [ 4, 5, 6 ] ]; // third row
21
22 outputArray( "Values in array1 by row" , array1 );
23 outputArray( "Values in array2 by row" , array2 );
24 }
Arrayarray1provides six initializers in
two rows.
Arrayarray2provides six initializers in
three rows.
Function outputArraydisplays each array’s
elements in a Web page.
Outline
InitArray3.html
(2 of 2)25
26 function outputArray( header, theArray )
27 {
28 document.writeln( "<h2>" + header + "</h2><tt>" );
29
30 for ( var i in theArray ) {
31
32 for ( var j in theArray[ i ] )
33 document.write( theArray[ i ][ j ] + " " );
34
35 document.writeln( "<br />" );
36 }
37
38 document.writeln( "</tt>" );
39 }
40 // -->
41 </script>
42
43 </head><body onload = "start()"></body>
44 </html>
Referencing the multidimensional
array theArray.
InitArray3.html
(2 of 2)25
26 function outputArray( header, theArray )
27 {
28 document.writeln( "<h2>" + header + "</h2><tt>" );
29
30 for ( var i in theArray ) {
31
32 for ( var j in theArray[ i ] )
33 document.write( theArray[ i ][ j ] + " " );
34
35 document.writeln( "<br />" );
36 }
37
38 document.writeln( "</tt>" );
39 }
40 // -->
41 </script>
42
43 </head><body onload = "start()"></body>
44 </html>
Referencing the multidimensional
array theArray.
Multidimensional Arrays
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