Lecture 6 Footnotes& Answers

IS4 030 - Website Design for e-Commerce By SMIEEE, SMACM, MACS E-mail: [email_address] Room: P7919 Consultation Hours: 3:30 - 5:30pm Monday Lecture Six –JavaScript I

Validating Forms
Data entered by users should always be validated!
Validation should take place in the browser for speed , but also on the server as well e.g., if a user is a registered Web site client
Question
Could we use JavaScript to check if a user is a registered user for a Web site e.g., a valid student a/c at CityU?

Validating Forms
Basic validation program codes (e.g., checking a field is blank or not) can be written in JavaScript, VBScript or Java Server Page, ASP.NET , but JavaScript is preferred. Why??
Form should have a name attribute so you can access the fields by using computer programs (e.g., JavaScript, ASP .Net, etc.)

What is a Function?
A function is an operation that can return a value.
e.g., Sin(90) = 1, Sin is a function and 1 is the value return by the function.
Some Script languages such as JavaScript use pre-defined functions to carry out Web page display/validation operations.
The difference between scripting language (e.g., Javascript) and full computer language (e.g., Java)?

Object-Base Script Language
Properties are the values associated with an object
e.g., “txt” is an object and “length” is its property
<html>
<body>
<script type="text/javascript">
var txt="Hello World!"
document.write( txt.length )
</script>
</body>
</html>
What will be the output from the Browser?

Lecture 6 Footnotes& Answers

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