javascript - locking a textarea using jQuery? - Stack Overflow

admin管理员组

文章数量:1416050

How do I "lock" a textarea with jQuery so that no more characters can be entered? I don't want to necessarily disable it since I want to allow characters to be deleted.

update: oops..it just came to me: if I am limiting the length to say 400 characters then i can use the following when the length is > 400:

this.value = this.value.substring(0, 400);

which will just trim the excess

How do I "lock" a textarea with jQuery so that no more characters can be entered? I don't want to necessarily disable it since I want to allow characters to be deleted.

update: oops..it just came to me: if I am limiting the length to say 400 characters then i can use the following when the length is > 400:

this.value = this.value.substring(0, 400);

which will just trim the excess

• javascript
• jquery

Share Improve this question Follow edited Aug 20, 2009 at 4:29 oym asked Aug 20, 2009 at 4:19 oymoym 7,0831717 gold badges6464 silver badges8989 bronze badges 2

• 1 Just a point about all the solutions below: none of them prevent mouse-based copy-paste into a textarea. – Joe Chung Commented Aug 20, 2009 at 4:49
• 1 Also, be sure that you validate the character count server-side. Client-side validation isn't safe. – sjstrutt Commented Aug 20, 2009 at 5:26

Add a ment  | 

4 Answers 4

Sorted by: Reset to default 3

following is quick contraption from modification of jquery.numeric plugin :)

It allows special keys but don't let user type anything.

<textarea id="txt" rows="5" cols="50"></textarea>

<script type="text/javascript">
$(document).ready(function(){
   $("#txt").keypress(function(e){
         var key = e.charCode ? e.charCode : e.keyCode ? e.keyCode : 0;
         // allow Ctrl+A
         if((e.ctrlKey && key == 97 /* firefox */) || (e.ctrlKey && key == 65) 
                                     /* opera */) return true;
         // allow Ctrl+X (cut)
         if((e.ctrlKey && key == 120 /* firefox */) || (e.ctrlKey && key == 88) 
                                     /* opera */) return true;
         // allow Ctrl+C (copy)
         if((e.ctrlKey && key == 99 /* firefox */) || (e.ctrlKey && key == 67) 
                                     /* opera */) return true;
         // allow Ctrl+Z (undo)
         if((e.ctrlKey && key == 122 /* firefox */) || (e.ctrlKey && key == 90) 
                                     /* opera */) return true;
         // allow or deny Ctrl+V (paste), Shift+Ins
         if((e.ctrlKey && key == 118 /* firefox */) || (e.ctrlKey && key == 86) 
                                     /* opera */
         || (e.shiftKey && key == 45)) return true;
         //page up, down, home end, left-right-up-down
         if(key > 32 && key < 40) return true;

         // if DEL or BACKSPACE is pressed
         return key == 46 || key == 8;

   });
});
</script>

Try this:

$("textarea").keypress(function(){ 
  if($(this).val().length>=10) 
    return false; 
});

Demo here: http://jsbin./erama

You could bind to the keypress/keydown event of the textarea and block out all characters except backspace and delete. This way the user can delete characters but can't add/remove new characters.

You bind to the keypress event like this:

$('#text-area').keypress(function(e) {});

Then you can use the keyCode property of the event object (argument e) that is passed to check if the pressed key is delete or backspace. You can find more information on the keypress event on the jquery website.

You can base yourself on a list of keycodes to only allow delete and backspace. In this case keyCode should be equal to 8 or 46.

So the resulting code would be something like this (not tested though):

$('#text-area').keypress(function(e) { if(e.keyCode != 8 && e.keyCode != 46) { e.preventDefault(); } }); 

The preventDefault function of the event will stop any further processing, so if the characters is not delete or backspace it will not be typed.

Here is plugin to limit input to textboxes/textareas

    jQuery.fn.charlimit = function(prompt, limit) {
        this.keyup(function(e) {
            var txt = $(this).val();
            var c = txt.length;

            if (prompt != null || prompt != 'undefined') {
                $(prompt).html((limit - c) + " chars left.");
            }
            if (c > limit) {
                $(this).val(txt.substring(0, limit));
                return false;
            }
            return true;
        });
        return this;
    }

prompt can be any span/div etc to show prompt message.

本文标签： javascriptlocking a textarea using jQueryStack Overflow