We know that the text box can have a MaxLength property, you can limit the length of the text box, when the note box is not textarea, then how to limit the length of the note box? In fact, it's very simple, only to add to this sentence
On it, the whole wording is as follows:
<textarea name= "A" cols= "A" rows= "2" >aaaa</textarea>
We can also write the judgment in the function, and if the length of the input exceeds the display, the message is displayed as follows:
<body>
<form name = "Testform" >
<textarea name= "A" cols= "A" rows= "2" >aaaa</textarea>
<input type= "button" onclick = "checkvalid ()" value= "Submit" >
</form>
</body>
<script language= "JavaScript" >
function Checkvalid ()
{
var a = DOCUMENT.TESTFORM.A;
if (A.value.length > 20)
{
Alert ("The length of the note box entered cannot exceed 20 characters!");
return false;
}
return true;
}