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Typical form data verified by JavaScript includes:
Have you entered required items in the form?
Is the email address entered by the user valid?
Have you entered a valid date?
Does the user input text in the data field (numeric field?
Required (or required) project
The following function is used to check whether the user has entered a required (or required) project in the form. If required or required, the warning box is displayed, and the return value of the function is false. Otherwise, the return value of the function is true (meaning there is no data problem ):
Copy codeThe Code is as follows:
Function validate_required (field, alerttxt)
{
With (field)
{
If (value = null | value = "")
{Alert (alerttxt); return false}
Else {return true}
}
}
Email verification (verify email)
The following function checks whether the input data conforms to the basic syntax of the email address.
That is to say, the input data must contain the @ symbol and the dot (.). At the same time, @ cannot be the first character of the email address, and @ must have at least one dot:
Copy codeThe Code is as follows:
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}
}
}
Instance:
Copy codeThe Code is as follows:
<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}
}
}
Function validate_form (thisform)
{
With (thisform)
{
If (validate_email (email, "Not a valid e-mail address! ") = False)
{Email. focus (); return false}
}
}
</Script>
</Head>
<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>
</Html>
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