Limit the number of text bytes. js Code

Write a piece of js for you when you are working on the project. The limit on the number of characters in text is frequently used in actual development. The main problem is the restriction on Chinese characters. The code below solves the problem of the limit on the number of bytes; you only need to save the code to a js file and introduce it to the verification page! At the same time, I hope you can give us great support and valuable comments. I will post more articles in the future when I am idle. Thank you !!

/*
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: <textarea name = "explain" id = "explain" onkeyup = "limitLength (value, 5, 'semantic description', 'explain ')">

Or

<Input type = "text" name = "explain" id = "explain" onkeyup = "limitLength (value, 5, 'semantic description', 'explain ')">

*/

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;
}