“I have powerful CGI and PHP scripts on my server!”.
Do you need to open a PopUp or PopUnder window when your website visitor enters or leaves your site?
Do you need to validate a form before it’s submitted to a server?
<head>...</head> tag pair in the HTML of your page. This is because the HEAD-section of a document is read first whilst the page loading.
The first thing a web browser will seen when looking at this page is this…
This attribute is used for browsers compatibility.
Then after this the HTML-comment
<!-- ... //--> tag pair is used.
You can even use a script-file on another server like this…
You can connect the occurrence of an event to some function that carries out tasks for that event. Events are said to be bound to an element. You instruct an element to be on the lookout for an event of a particular type that comes its way. For example, you can instruct a button to respond to a mouse click on it, while all surrounding elements ignore clicks on them.
Syntax for event binding takes on many forms, but the basic task for the scripter is to assign a function to a particular event of a particular element. The assignment statement is called an event handler. Thus, when the user clicks on a button that has pre-assigned the
handleClick( ) function to the click event, that event handler function runs whenever the user clicks on the button.
Each HTML-tag has a predefined number of events. When you refer to an event in your scripting, you typically use a one-word reference that is the name of the event preceded by on. Therefore, when a button receives a click event, it looks to see if it has an
onclick event handler assigned to it; if so, the event handler function starts executing immediately.
<input type="button" value="ClickMe!" onclick="myFunction()">
<img src="grayDot.gif" onmouseover="this.src=redDot.gif" onmouseout="this.src=grayDot.gif">
A traditional HTML form submits its data to a program running on the server. Client-side form validation is a helpful service that speeds the correction of potential errors in forms before they ever reach the server.
That is not meant to imply that client-side validation can replace server-side validation, far from it.
Submission is aborted if the event handler evaluates to return false.
Include the return statement in the event handler assignment, and let the validation function supply the Boolean value based on its findings:
When a new page loads into the browser, you want to execute script statements to open your PopUp window.
The onload event of the window object fires after all content and processes coded in the HTML have finished loading and self-initializing. Use this event to trigger your function.
All scriptable browsers support the following syntax: