TextArea sets the maximum input value of the MaxLength attribute js code

The MAXLENGTH attribute of TEXTAREA in standard DHTML documents does not work by default and only works when an event occurs
As follows: http://spiderscript.net/site/spiderscript/examples/ex_textarea_maxlength.asp
But there is and works in TEXT ,
So how to realize that the input content cannot exceed how many characters in TEXTAREA?

Method 1, if you only need to intercept the content of a few characters, you can:

Copy code The code is as follows:

Method 2,

Copy code The code is as follows:

This method uses the truncation method. When the last character is entered, if you enter again, the cursor will flash. But it can solve the length limit problem of using CTRL C to copy, but it still doesn't work if you use the mouse to copy.

Method 3, this method directly determines the length of the input

Copy code The code is as follows :

When the input content is greater than 15, because it returns false, this implementation will not show the problem of cursor flickering, but it does not solve the copied length. The limitation problem is that the copied content can exceed the maximum length limit
return (Object.value.length <=MaxLen); but I tested and found that when the number of bytes entered =maxlen, one character can be entered, so I changed it to return (Object.value.length
Method 4. In fact, method 4 is a further optimization based on method 2 and method 3. Objectively speaking, methods 2 and 3 only do part of the work

Copy the code The code is as follows:

cols="45" <BR>rows="3" <BR>wrap="virtual" <BR>onkeypress="return(this.value.length<20)" <BR>onkeydown="textlen(this,20)" <BR>onkeyup="textlen(this,20)" <BR>onblur="maxtext (this,20)" <BR>> <br><br>The above method adds the onblur event on the original basis, which is mainly used to deal with the problem when the user completes the transfer of text by copying and pasting instead of inputting. It is actually a combination of Method 2 and Method 3. The following is the result of adding and using the maxlength attribute for TextArea and combining it with the above example:<html><head><script type="text/javascript">function ismaxlength(obj){var mlength=obj.getAttribute? parseInt(obj.getAttribute("maxlength")): ""if (obj.getAttribute && obj.value.length>mlength)alert('This text box allows the input of a maximum length of 'mlength' characters, and the content beyond the limit will be Truncate ")obj.value=obj.value.substring(0,mlength)}function imposeMaxLength(obj){ var mlength=obj.getAttribute? parseInt(obj.getAttribute("maxlength")) : "" return (obj.value .length <mlength);}</script></head><body><form name="myform"> <textarea maxlength="5" onkeypress="return imposeMaxLength(this)" onblur ="ismaxlength(this)">

Javascript code
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Copy code The code is as follows:

 
function SetTextAreaMaxLength(controlId,length) 
{ 
// JScript File for TextArea 
// Keep user from entering more than maxLength characters 
function doKeypress(control,length){ 
maxLength = length; 
value = control.value; 
if(maxLength && value.length > maxLength-1){ 
event.returnValue = false; 
maxLength = parseInt(maxLength); 
} 
} 
// Cancel default behavior 
function doBeforePaste(control,length){ 
maxLength = length; 
if(maxLength) 
{ 
event.returnValue = false; 
} 
} 
// Cancel default behavior and create a new paste routine 
function doPaste(control,length){ 
maxLength = length; 
value = control.value; 
if(maxLength){ 
event.returnValue = false; 
maxLength = parseInt(maxLength); 
var oTR = control.document.selection.createRange(); 
var iInsertLength = maxLength - value.length   oTR.text.length; 
var sData = window.clipboardData.getData("Text").substr(0,iInsertLength); 
oTR.text = sData; 
} 
} 
function doDragenter(control,length) 
{ 
maxLength = length; 
value = control.value; 
if(maxLength){ 
event.returnValue = false; 
} 
} 
function addEvent(elm, evType, fn, useCapture) 
{ 
if (elm.addEventListener) 
{ 
elm.addEventListener(evType, fn, useCapture); 
return true; 
} 
else if (elm.attachEvent) 
{ 
var r = elm.attachEvent('on'   evType, fn); 
return r; 
} 
else { 
elm['on'   evType] = fn; 
} 
} 
function AttacheventTextAreaBeforePaste(obj,length) 
{ 
return function() 
{ 
doBeforePaste(obj,length) 
} 
} 
function AttacheventTextAreaPaste(obj,length) 
{ 
return function() 
{ 
doPaste(obj,length) 
} 
} 
function AttacheventTextAreaKeyPress(obj,length) 
{ 
return function() 
{ 
doKeypress(obj,length) 
} 
} 
function AttacheventTextAreaDragEnter(obj,length) 
{ 
return function() 
{ 
doDragenter(obj,length); 
} 
} 
var obj = document.getElementById(controlId); 
addEvent(obj,'keypress',AttacheventTextAreaKeyPress(obj,length),null); 
addEvent(obj,'beforepaste',AttacheventTextAreaBeforePaste(obj,length),null); 
addEvent(obj,'paste',AttacheventTextAreaPaste(obj,length),null); 
addEvent(obj,'dragenter',AttacheventTextAreaDragEnter(obj,length),null); 
} 
function SetTextAreaMaxLength(controlId,length) 
{ 
// JScript File for TextArea 
// Keep user from entering more than maxLength characters 
function doKeypress(control,length){ 
maxLength = length; 
value = control.value; 
if(maxLength && value.length > maxLength-1){ 
event.returnValue = false; 
maxLength = parseInt(maxLength); 
} 
} 
// Cancel default behavior 
function doBeforePaste(control,length){ 
maxLength = length; 
if(maxLength) 
{ 
event.returnValue = false; 
} 
} 
// Cancel default behavior and create a new paste routine 
function doPaste(control,length){ 
maxLength = length; 
value = control.value; 
if(maxLength){ 
event.returnValue = false; 
maxLength = parseInt(maxLength); 
var oTR = control.document.selection.createRange(); 
var iInsertLength = maxLength - value.length   oTR.text.length; 
var sData = window.clipboardData.getData("Text").substr(0,iInsertLength); 
oTR.text = sData; 
} 
} 
function doDragenter(control,length) 
{ 
maxLength = length; 
value = control.value; 
if(maxLength){ 
event.returnValue = false; 
} 
} 
function addEvent(elm, evType, fn, useCapture) 
{ 
if (elm.addEventListener) 
{ 
elm.addEventListener(evType, fn, useCapture); 
return true; 
} 
else if (elm.attachEvent) 
{ 
var r = elm.attachEvent('on'   evType, fn); 
return r; 
} 
else { 
elm['on'   evType] = fn; 
} 
} 
function AttacheventTextAreaBeforePaste(obj,length) 
{ 
return function() 
{ 
doBeforePaste(obj,length) 
} 
} 
function AttacheventTextAreaPaste(obj,length) 
{ 
return function() 
{ 
doPaste(obj,length) 
} 
} 
function AttacheventTextAreaKeyPress(obj,length) 
{ 
return function() 
{ 
doKeypress(obj,length) 
} 
} 
function AttacheventTextAreaDragEnter(obj,length) 
{ 
return function() 
{ 
doDragenter(obj,length); 
} 
} 
var obj = document.getElementById(controlId); 
addEvent(obj,'keypress',AttacheventTextAreaKeyPress(obj,length),null); 
addEvent(obj,'beforepaste',AttacheventTextAreaBeforePaste(obj,length),null); 
addEvent(obj,'paste',AttacheventTextAreaPaste(obj,length),null); 
addEvent(obj,'dragenter',AttacheventTextAreaDragEnter(obj,length),null); 
} 

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HTML code

코드 복사 코드는 다음과 같습니다.

 
TextMode="MultiLine" Height="113px" MaxLength="10"> 
<스크립트 언어= "javascript" type="text/javascript"> 
SetTextAreaMaxLength('<%=TextBoxAddress.ClientID %>',10) 
 

TextArea sets the maximum input value of the MaxLength attribute js code_javascript skills