Post on 13-May-2015
INFSCI 1052
Client Side versus Server Side Server side
• PHP, ASP, Cold Fusion, Ruby on Rails• Good for accessing databases
Client Side• Good for immediacy of action• Forms• WebPages• Also, Flash, Ajax
Compiled versus interpreted languages• C, C#, JAVA, • JS, PHP, Python
Adding JS to a webpage• Usually add to the <head> section• Can be added to the <body> section too• Can be linked to an external JS file
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html;
charset=utf-8" /> <title>Untitled Document</title> </head> <script type="text/javascript"> alert('helloworld'); </script> <body> </body> </html>
External Linking to JS File- Two separate lines
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Untitled Document</title>
<script type="text/javascript" src="myprogram.js"> </script>
<script type="text/javascript"> alert('helloworld'); </script> </head>
<body> </body> </html>
Good JavaScript Tutorial http://www.hunlock.com/blogs/Essential_Javascript_--_A_Javascript_Tutorial
Linking and paths• Absolute paths
http://www.sis.pitt.edu
• Root-relative paths Using a webserver Relative to the site’s top level folder
Ex. /myfolder/index.html
• Document-relative paths Specifies path from Web page to the JS file
Ex: ../myscripts/myjsfile.js
JavaScript:The Missing Manual http://www.sawmac.com/missing/java
script/tutorials/index.php http://www.sawmac.com/missing/java
script/tutorials/examples/index.html Completed tutorials section and
working tutorials Focus is on basic JS and using JS
libraries such as JQuery.
Writing text to a web page• Document.write (‘<p> Hello World </P’);• http://www.sawmac.com/missing/javascript/t
utorials/examples/chapter01/complete_1.2.html
Attaching external file http://www.sawmac.com/missing/java
script/tutorials/examples/chapter01/complete_1.3.html
Errors and debugging• If error in code typically nothing happens
Web Browsers have consoles that can display JS errors
Firefox has better console than IE• Lists type of error, name of file, and line
number• Select Tools->Error Console
Common Errors• Missing semicolon, missing quote mark,
misspelled word, missing ), unterminated string literal, missing }
Statement: the basic unit of JS program, ends in semicolon
Data Types• Number
Integer or fractional• String
Use quote marks• Boolean
True or False Variables
• var varname; Begin with letter, $, or __ Can only contain letters, numbers, $ and __ CaSE SENSITIVE
Var Examples• var number=0;• var name=‘Bob’;• var age=26;• var open=true;
Math operators and order of operations apply• +, -, *, / • Use parenthesis to ensure correct order of
operations
Addition and concatenation• + sign for both purposes• When adding two numbers the + sign does
addition• When “adding” two string or a number and a
string then the concatenation function is performed Ex. var fname = ‘Bill’; var lname = ‘Smith’; var totalname=fname+lname;Sample:
http://www.sawmac.com/missing/javascript/tutorials/examples/chapter02/complete_2.1.html
Arrays• var months = [‘Jan’, ‘Feb’, ‘Mar’];• var months = new Array(‘Jan’, ‘Feb’, ‘Mar’];• Empty array
var months =[];• Accessing arrays
nameofarray[#]; Zero based so nameofarray[2] references the third
element• Adding element to end of array
nameofarray[nameofarray.length] = ‘text’; var colors = [‘red’, ‘blue’, green’]
colors [colors.length]=‘purple’;
Arrays• Push command to add multiple elements to the end of the array
colors.push(‘pink’, orange’, ‘brown’);• Add to the beginning of an array
.unshift• Push and unshift return a value: the number of items in the
array• Removing items in an array
pop() – removes the last item shift() – removes the first item Ex. var x = [0,1,2,3]; var removeditem = x.pop()
• Adding and deleting in middle of array splice function
• Sample: http://www.sawmac.com/missing/javascript/tutorials/examples/chapter02/complete_2.3.html
Logic
If (condition) {Code statements}
• Comparison operators>, <, >=, <=
• If else and if else if• && = and • || = or• ! = not• Sample:
http://www.sawmac.com/missing/javascript/tutorials/examples/chapter03/complete_3.1.html
Loops• While
while (condition) {JS statements
}
• For Loopsfor (var=x, x<=100; x++) {
JS statements}
Do While Loopsdo {
JS statements} while (condition);
FunctionsFunction functionName() {
JS Statements}
Sample: http://www.sawmac.com/missing/
javascript/tutorials/examples/chapter03/complete_3.2.html More with using the Date object
http://www.elated.com/articles/working-with-dates/
Send information to functions via arguments and paramaters
function functionName ( paramater 1, paramater2) {JS Statements};
functionName (argument1, argument2);
• Retrieving Information from functions• Function functionName (paramater1, paramater2) {• JS statements• Return value; • }
• Sample: http://www.sawmac.com/missing/javascript/tutorials/examples/chapter03/complete_3.3.html
DOM• Document Object Model• Working with Web pages
Identify an element on a page Do something with the element
Add/remove a class attribute Change a property of the element Add new content Remove the element Extract information from the element
Provides the information that JS needs to interact with elements on the webpage
A navigation structure or map of the elements on the webpage
Standard from the W3C• Most browsers have adopted but in different
ways Hierarchical structure of the tags in a
web page
Tags• Parents• Chidren• Siblings• All nodes• Text is nodes too• Nesting determines the relationships
Selecting a page element• getElementById()
Locating a single element that has a unique ID Document.getElementById(‘header’)
Searches page for a tag with an ID of ‘header’ Typically the results of this action are stored in a variable
var headNode=document.getElementById(‘header’);
GetElementsByTagName• Document.getElementsByTagName (‘a’);
Usually stored in a var var myLinks=document.getElementsByTagName
(‘a’); Find all <a> tags and store results in a var named
myLinks This action returns a list of nodes instead of a single
node Similar to arrays
Can access a single node using index notation Can use the length property Can loop using a for loop
Accessing near by nodes• .childNodes
A property of a node Ex.
var headline = Document.getElementById(‘header’);var headlineChildren = headline.childNodes;
• .parentNode• A property that represents the direct parent of a node
• .nextSibling and .previousSibling• Properties that access next and previous siblings
• .innerHTML Not a standard part of DOM but most browsers implement it Accesses the text part of a node
Examplevar pTags = document.getElementsByTagName(‘p’);
var theP = pTags[0]; alert(theP.innerHTML);
Opens an alert box and prints out the text of the first paragraph.