Event Handlers

Web pages are active and interactive, files and images load in, the user can move between frames and windows, can enter text, can make selections and click on buttons. These events can be picked up by the system and used to start javscript code. These are called event handlers.

There are dozens of event handlers but these 6 are what you will be useing most often:

• onClick ~ applies to buttons, checkboxes and selection elements on forms. It is activated by a click on the left mouse button
• onFocus ~ applies to all screen objects and is activated when an object comes "into focus". In the case of a window, this means when it is opened or reopened; for a form element, it means initially the topmost element (top or first form field), and then the one the user moves onto by pressing the [tab] key or clicking the mouse.
• onBlur ~ also applies to screen objects and is activated when the object goes out of focus.
• onChange ~ applies to text and textarea elements in a form and picks up each keystroke.
• onMouseOver ~ applies to links and areas of image maps which can also carry links. It is activated when a mouse cursor passes over the object.
• onMouseOut ~ also applies to links and areas and is activated when the mouse cursor moves off the object.

What ever the event handler, the code is attached in the same way ~ enclosed the code in "double quotes", assign it with an = sign and put the whole expression inside the tag that creates the object.

If the code you are using contains text (such as in an alert message), it will need to be enclosed in 'single quotes'. If you are going to be enclosing several javascript statements to one event each one will need to be seperated by a semi colon ; and the whole code enclosed in "double quotes" as usual.

onClick="checkEntry(); alert('Thank You')"

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