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<p>From <b>http://www.w3schools.com</b> (Copyright Refsnes Data)</p>
<h1>JavaScript Form Validation</h1><a href="js_cookies.asp"><img alt="previous" border="0" src="../images/btn_previous.gif" width="100" height="20" /></a>
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<p class="intro">JavaScript can be used to validate input data in HTML forms before
sending off the content to a server.</p>
<hr />
<h2>JavaScript Form Validation</h2>
<p>JavaScript can be used to validate input data in HTML forms before sending off the
content to a server.</p>
<p>Form data that typically are checked by a JavaScript could be:</p>
<ul>
<li>has the user left required fields empty?</li>
<li>has the user entered a valid e-mail address?</li>
<li>has the user entered a valid date?</li>
<li>has the user entered text in a numeric field?</li>
</ul>
<hr />
<h2>Required Fields</h2>
<p>The function below checks if a required field has been left empty. If the
required field is blank, an alert box alerts a message and the function returns
false. If a value is entered, the function returns true
(means that data is OK):</p>
<table class="ex" cellspacing="0" border="1" width="100%" id="table7"><tr><td>
<pre>function validate_required(field,alerttxt)
{
with (field)
{
if (value==null||value=="")
{
alert(alerttxt);return false;
}
else
{
return true;
}
}
}</pre>
</td></tr></table>
<p>The entire script, with the HTML form could look something like this:</p>
<table class="ex" cellspacing="0" border="1" width="100%" id="table8"><tr><td>
<pre><html>
<head>
<script type="text/javascript">
function validate_required(field,alerttxt)
{
with (field)
{
if (value==null||value=="")
{alert(alerttxt);return false;}
else {return true}
}
}</pre>
<pre>function validate_form(thisform)
{
with (thisform)
{
if (validate_required(email,"Email must be filled out!")==false)
{email.focus();return false;}
}
}
</script>
</head></pre>
<pre><body>
<form action="submitpage.htm"
onsubmit="return validate_form(this)"
method="post">
Email: <input type="text" name="email" size="30">
<input type="submit" value="Submit">
</form>
</body></pre>
<pre></html></pre>
</td></tr></table>
<br />
<hr />
<h2>E-mail Validation</h2>
<p>The function below checks if the content has the general syntax of an email.</p>
<p>This means that the input data must contain at least an @ sign and a dot (.).
Also, the @ must not be the first character of the email address, and the last
dot must at least be one character after the @ sign:</p>
<table class="ex" cellspacing="0" border="1" width="100%" id="table1"><tr><td>
<pre>function validate_email(field,alerttxt)
{
with (field)
{
apos=value.indexOf("@");
dotpos=value.lastIndexOf(".");
if (apos<1||dotpos-apos<2)
{alert(alerttxt);return false;}
else {return true;}
}
}</pre>
</td></tr></table>
<p>The entire script, with the HTML form could look something like this:</p>
<table class="ex" cellspacing="0" border="1" width="100%" id="table2"><tr><td>
<pre><html>
<head>
<script type="text/javascript">
function validate_email(field,alerttxt)
{
with (field)
{
apos=value.indexOf("@");
dotpos=value.lastIndexOf(".");
if (apos<1||dotpos-apos<2)
{alert(alerttxt);return false;}
else {return true;}
}
}</pre>
<pre>function validate_form(thisform)
{
with (thisform)
{
if (validate_email(email,"Not a valid e-mail address!")==false)
{email.focus();return false;}
}
}
</script>
</head></pre>
<pre><body>
<form action="submitpage.htm"
onsubmit="return validate_form(this);"
method="post">
Email: <input type="text" name="email" size="30">
<input type="submit" value="Submit">
</form>
</body></pre>
<pre></html></pre>
</td></tr></table>
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<p>From <b>http://www.w3schools.com</b> (Copyright Refsnes Data)</p>
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