Limit the number of text bytes in form. js code_form special effect

JavaScript code that limits the number of text bytes in form /*
Value: value;
ByteLength: Database Byte Length
Title: Chinese name of the field
Attribute: attribute name
Usage instructions:

Add (1) onkeyup = "limitLength (this. value, 100, 'name', 'name ')"
(2) id = "name" or [struts tag] styleId = "name"
Note: The id and attribute names must be the same.

Example:

Or



*/



Function limitLength (value, byteLength, title, attribute ){
Var newvalue = value. replace (/[^ \ x00-\ xff]/g ,"**");
Var length = newvalue. length;

// When the number of bytes entered is smaller than the set number of bytes
If (length * 1 <= byteLength * 1 ){
Return;
}
Var limitDate = newvalue. substr (0, byteLength );
Var count = 0;
Var limitvalue = "";
For (var I = 0; I <limitDate. length; I ++ ){
Var flat = limitDate. substr (I, 1 );
If (flat = "*"){
Count ++;
}
}
Var size = 0;
Var istar = newvalue. substr (byteLength * 1-1, 1); // check whether the checkpoint is "×"

// If the base point is X; determines whether X is an even number or an odd number within the base point.
If (count % 2 = 0 ){
// When the value is an even number
Size = count/2 + (byteLength * 1-count );
Limitvalue = value. substr (0, size );
} Else {
// When the value is an odd number
Size = (count-1)/2 + (byteLength * 1-count );
Limitvalue = value. substr (0, size );
}
Alert (title + "maximum input" + byteLength + "bytes (equivalent to" + byteLength/2 + "Chinese characters )! ");
Document. getElementById (attribute). value = limitvalue;
Return;
}