Javascript form verification control code

1. length limit
<SCRIPT>
Function Test ()
{
If (document. A. B. value. length> 50)
{
Alert ("cannot exceed 50 characters! ");
Document. A. B. Focus ();
Return false;
}
}
</SCRIPT>
<Form name = A onsubmit = "return test ()">
<Textarea name = "B" Cols = "40" Wrap = "virtual" rows = "6"> </textarea>
<Input type = "Submit" name = "Submit" value = "check">
</Form>
2. Only Chinese characters are allowed
<Input onkeyup = "value ="/oblog/value. Replace (/[^ \ u4e00-\ u9fa5]/g, '')">
3. English only
<Script language = JavaScript>
Function onlyeng ()
{
If (! (Event. keycode> = 65 & event. keycode <= 90 ))
Event. returnvalue = false;
}
</SCRIPT>
<Input onkeydown = "onlyeng ();">
4. Only numbers are allowed.
<Script language = JavaScript>
Function onlynum ()
{
If (! (Event. keycode> = 48 & event. keycode <= 57) | (event. keycode> = 96 & event. keycode <= 105 )))
// Consider the numeric keys on the keypad
Event. returnvalue = false;
}
</SCRIPT>
<Input onkeydown = "onlynum ();">
5. Only English characters and numbers are allowed.
<Input onkeyup = "value ="/oblog/value. Replace (/[\ W]/g ,"'')"
Onbeforepaste = "clipboardData. setdata ('text', clipboardData. getdata ('text'). Replace (/[^ \ D]/g,'') ">
6. Verify the email format
<Script language = JavaScript runat = Server>
Function isemail (stremail ){
If (stremail. search (/^ \ W + (-\ W +) | (\. \ W +) * \ @ [A-Za-z0-9] + ((\. |-) [A-Za-z0-9] + )*\. [A-Za-z0-9] + $ /)! =-1)
Return true;
Else
Alert ("oh ");
}
</SCRIPT>
<Input type = text onblur = isemail (this. Value)>
7. Shielding keywords (here, shielding ***** and ****)
<Script language = "javascript1.2">
Function Test (){
If (. b. value. indexof ("***") = 0) | (. b. value. indexof ("***") = 0 )){
Alert (":)");
A. B. Focus ();
Return false ;}
}
</SCRIPT>
<Form name = A onsubmit = "return test ()">
<Input type = text name = B>
<Input type = "Submit" name = "Submit" value = "check">
</Form>
8. Whether the two passwords are the same
<Form method = post action = "">
<Input type = "password" id = "input1">
<Input type = "password" id = "input2">
<Input type = "button" value = "test" onclick = "check ()">
</Form>
<SCRIPT>
Function check ()
{
With (document. All ){
If (input1.value! = Input2.value)
{
Alert ("false ")
Input1.value = "";
Input2.value = "";
}
Else document. Forms [0]. Submit ();
}
}
</SCRIPT>
Enough.
9. Blocking right-click is cool
Oncontextmenu = "Return false" ondragstart = "Return false" onselectstart = "Return false"
Add to Body

II
2.1 Form items cannot be blank
<Script language = "JavaScript">
<! --
Function checkform ()
{
If (document. Form. Name. value. Length = 0 ){
Alert ("enter your name! ");
Document. Form. Name. Focus ();
Return false;
}
Return true;
}
-->
</SCRIPT>
2.2 compare whether the values of the two form items are the same
<Script language = "JavaScript">
<! --
Function checkform ()
If (document. Form. pwd. value! = Document. Form. pwd_again.value ){
Alert ("the password you entered twice is different! Enter again .");
Document. adduser. pwd. Focus ();
Return false;
}
Return true;
}
-->
</SCRIPT>
2.3 form items can only be numbers and "_", used for phone/Bank Account Verification, and can be extended to domain name registration.
<Script language = "JavaScript">
<! --
Function isnumber (string)
{
VaR letters = "1234567890-"; // you can add input values by yourself.
VaR I;
VaR C;
If (string. charat (0) = '-')
Return false;
If (string. charat (string. Length-1) = '-')
Return false;
For (I = 0; I <string. length; I ++)
{
C = string. charat (I );
If (letters. indexof (c) <0)
Return false;
}
Return true;
}
Function checkform ()
{
If (! Isnumber (document. Form. Tel. Value )){
Alert ("your phone number is invalid! ");
Document. Form. Tel. Focus ();
Return false;
}
Return true;
}
-->
</SCRIPT>

2.4 form entry input value/length limit
<Script language = "JavaScript">
<! --
Function checkform ()
{
If (document. Form. Count. value> 100 | document. Form. Count. value <1)
{
Alert ("the input value cannot be less than zero or greater than 100! ");
Document. Form. Count. Focus ();
Return false;
}
If (document. Form. Message. value. Length <10)
{
Alert ("the input text is less than 10! ");
Document. Form. Message. Focus ();
Return false;
}
Return true;
}
// -->
</SCRIPT>