Page 155 - CITS - Computer Software Application -TT

COMPUTER SOFTWARE APPLICATION - CITS

form.addEventListener(“submit”, function (event) {

// stop form submission
event.preventDefault();
// validate the form
let nameValid = hasValue(form.elements[“name”], NAME_REQUIRED);
let emailValid = validateEmail(form.elements[“email”], EMAIL_REQUIRED, EMAIL_INVALID);

// if valid, submit the form.
if (nameValid && emailValid) {
alert(“Demo only. No form was posted.”);
}
});

Code language: JavaScript (javascript)
In the submit event handler:
1 Stop the form submission by calling the event.preventDefault() method.
2 Validate the name and email fields using the hasValue() and validateEmail() functions.
3 If both name and email are valid, show an alert. In a real-world application, you need to call the form.submit()
method to submit the form.
Summary
• Use the <form> element to create an HTML form.

• Use DOM methods such as getElementById() and querySelector() to select a <form> element. The document.
forms[index] also returns the form element by a numerical index.
• Use form.elements to access form elements.
• The submit event fires when users click the submit button on the form.

Concept of Cookies

Cookies let you store user information in web pages.
What are Cookies?
Cookies are data, stored in small text files, on your computer.
When a web server has sent a web page to a browser, the connection is shut down, and the server forgets
everything about the user.
Cookies were invented to solve the problem “how to remember information about the user”:
• When a user visits a web page, his/her name can be stored in a cookie.

• Next time the user visits the page, the cookie “remembers” his/her name.
Cookies are saved in name-value pairs like:
username = John Doe
When a browser requests a web page from a server, cookies belonging to the page are added to the request. This
way the server gets the necessary data to “remember” information about users.
None of the examples below will work if your browser has local cookies support turned off.
Create a Cookie with JavaScript
JavaScript can create, read, and delete cookies with the document.cookie property.
With JavaScript, a cookie can be created like this:

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CITS : IT&ITES - Computer Software Application - Lesson 37 - 46