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<h1>HTML DOM - Events</h1>
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<p class="intro">Events are actions that can be detected by JavaScript.</p>
<hr>
<h2>Events</h2>
<p>By using JavaScript, we have the ability to create dynamic web pages. Events
are actions that can be detected by JavaScript.</p>
<p>Every element on a web page has certain events which can trigger JavaScript
functions. For example, we can use the onClick event of a button element to
indicate that a function will run when a user clicks on the button. We define
the events in the HTML tags.</p>
<p>Examples of events:</p>
<ul>
<li>A mouse click</li>
<li>A web page or an image loading</li>
<li>Mousing over a hot spot on the web page</li>
<li>Selecting an input box in an HTML form</li>
<li>Submitting an HTML form</li>
<li>A keystroke </li>
</ul>
<p><b>Note:</b> Events are normally used in combination with functions, and the
function will not be executed before the event occurs!</p>
<p>For a complete reference of the events supported by the HTML DOM, see our
<a href="dom_obj_event.asp">HTML DOM Event reference</a>.</p>
<hr>
<h2>onload and onUnload</h2>
<p>The onload and onUnload events are triggered when the user enters or leaves
the page.</p>
<p>The onload event is often used to check the visitor's browser type and
browser version, and load the proper version of the web page based on the
information.</p>
<p>Both the onload and onUnload events are also often used to deal with cookies
that should be set when a user enters or leaves a page. For example, you could
have a popup asking for the user's name upon his first arrival to your page. The
name is then stored in a cookie. Next time the visitor arrives at your page, you
could have another popup saying something like: "Welcome John Doe!".</p>
<hr>
<h2>onFocus, onBlur and onChange</h2>
<p>The onFocus, onBlur and onChange events are often used in combination with
validation of form fields.</p>
<p>Below is an example of how to use the onChange event. The checkEmail()
function will be called whenever the user changes the content of the field:</p>
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