textarea character limit

问题

I would like to be able to limit the number of characters in a textarea. The method I am using works great in Google Chrome, but is slow in Firefox, and doesn\'t work in IE.

Javascript:

function len(){
  t_v=textarea.value;
  if(t_v.length>180){
    long_post_container.innerHTML=long_post;
    post_button.className=post_button.className.replace(\'post_it_regular\',\'post_it_disabled\');
    post_button.disabled=true;
  }
  else{
    long_post_container.innerHTML=\"\";
    post_button.className=post_button.className.replace(\'post_it_disabled\',\'post_it_regular\');
    post_button.disabled=false;
  }
  if(t_v.length>186){
        t_v=t_v.substring(0,186);
    }
}

HTML:

<textarea id=\"user_post_textarea\" name=\"user_post_textarea\" cols=\"28\" rows=\"1\"  onkeypress=\"len();\" onkeyup=\"len();\"></textarea>

Javascript at bottom of body element:

textarea=document.getElementById(\'user_post_textarea\');

回答1:

I found a good solution that uses the maxlength attribute if the browser supports it, and falls back to an unobtrusive javascript pollyfill in unsupporting browsers.

Thanks to @Dan Tello's comment I fixed it up so it works in IE7+ as well:

HTML:

<textarea maxlength="50" id="text">This textarea has a character limit of 50.</textarea>

Javascript:

function maxLength(el) {    
    if (!('maxLength' in el)) {
        var max = el.attributes.maxLength.value;
        el.onkeypress = function () {
            if (this.value.length >= max) return false;
        };
    }
}

maxLength(document.getElementById("text"));

Demo

There is no such thing as a minlength attribute in HTML5.
For the following input types: number, range, date, datetime, datetime-local, month, time, and week (which aren't fully supported yet) use the min and max attributes.

回答2:

~~This is entirely untested but it should do what you need.~~

Update : here's a jsfiddle to look at. Seems to be working. link

You would past it into a js file and reference it after your jquery reference. You would then call it like this..

$("textarea").characterCounter(200);

A brief explanation of what is going on..

On every keyup event the function is checking what type of key is pressed. If it is acceptable the the counter will check the count, trim any excess and prevent any further input once the limit is reached.

The plugin should handle pasting into the target too.

  ; (function ($) {
        $.fn.characterCounter = function (limit) {
            return this.filter("textarea, input:text").each(function () {
                var $this = $(this),
                  checkCharacters = function (event) {

                      if ($this.val().length > limit) {

                          // Trim the string as paste would allow you to make it 
                          // more than the limit.
                          $this.val($this.val().substring(0, limit))
                          // Cancel the original event
                          event.preventDefault();
                          event.stopPropagation();

                      }
                  };

                $this.keyup(function (event) {

                    // Keys "enumeration"
                    var keys = {
                        BACKSPACE: 8,
                        TAB: 9,
                        LEFT: 37,
                        UP: 38,
                        RIGHT: 39,
                        DOWN: 40
                    };

                    // which normalizes keycode and charcode.
                    switch (event.which) {

                        case keys.UP:
                        case keys.DOWN:
                        case keys.LEFT:
                        case keys.RIGHT:
                        case keys.TAB:
                            break;
                        default:
                            checkCharacters(event);
                            break;
                    }   

                });

                // Handle cut/paste.
                $this.bind("paste cut", function (event) {
                    // Delay so that paste value is captured.
                    setTimeout(function () { checkCharacters(event); event = null; }, 150);
                });
            });
        };
    } (jQuery));

回答3:

I think that doing this might be easier than most people think!

Try this:

var yourTextArea = document.getElementById("usertext").value;
// In case you want to limit the number of characters in no less than, say, 10
// or no more than 400.        
    if (yourTextArea.length < 10 || yourTextArea.length > 400) {
        alert("The field must have no less than 10 and no more than 400 characters.");
        return false;
    }

Please let me know it this was useful. And if so, vote up! Thx!

Daniel

回答4:

This works on keyup and paste, it colors the text red when you are almost up to the limit, truncates it when you go over and alerts you to edit your text, which you can do.

var t2= /* textarea reference*/

t2.onkeyup= t2.onpaste= function(e){
    e= e || window.event;
    var who= e.target || e.srcElement;
    if(who){
        var val= who.value, L= val.length;
        if(L> 175){
            who.style.color= 'red';
        }
        else who.style.color= ''
        if(L> 180){
            who.value= who.value.substring(0, 175);
            alert('Your message is too long, please shorten it to 180 characters or less');
            who.style.color= '';
        }
    }
}

回答5:

using maxlength attribute of textarea would do the trick ... simple html code .. not JS or JQuery or Server Side Check Required....

回答6:

Try using jQuery to avoid cross browser compatibility problems...

$("textarea").keyup(function(){
    if($(this).text().length > 500){
        var text = $(this).text();
        $(this).text(text.substr(0, 500));   
    }
});

回答7:

Quick and dirty universal jQuery version. Supports copy/paste.

$('textarea[maxlength]').on('keypress mouseup', function(){
    return !($(this).val().length >= $(this).attr('maxlength'));
});

回答8:

I believe if you use delegates, it would work..

$("textarea").on('change paste keyup', function () {
    var currText = $(this).val();
    if (currText.length > 500) {
        var text = $(this).text();
        $(this).text(text.substr(0, 500));
        alert("You have reached the maximum length for this field");
    }
});

回答9:

I have written my method for this, have fun testing it on your browsers, and give me feedback.

cheers.

function TextareaControl(textarea,charlimit,charCounter){
    if(
            textarea.tagName.toLowerCase() === "textarea" && 
            typeof(charlimit)==="number" &&
            typeof(charCounter) === "object" && 
            charCounter.innerHTML !== null
    ){
        var oldValue = textarea.value;
        textarea.addEventListener("keyup",function(){
            var charsLeft = charlimit-parseInt(textarea.value.length,10);
            if(charsLeft<0){
                textarea.value = oldValue;
                charsLeft = charlimit-parseInt(textarea.value.length,10);
            }else{
                oldValue = textarea.value;
            }
            charCounter.innerHTML = charsLeft;
        },false);
    }
}

回答10:

... onkeydown="if(value.length>500)value=value.substr(0,500); if(value.length==500)return false;" ...

It ought to work.

回答11:

  $(function()
	  {
	     $("#QtChar")[0].innerText = "Quantidade de Caracteres Restantes "+ parseInt($("#txtMensagem")[0].maxLength);
	  });
	  function tamanhoMensagem()
	  {
	     $("#QtChar")[0].innerText = "Quantidade de Caracteres Restantes "+ parseInt($("#txtMensagem")[0].maxLength - $("#txtMensagem").val().length);	
	  }

<html>
	<head>
	   <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
	</head>
	 <body>
	   <textarea id="txtMensagem" maxlength="10" onkeyup="tamanhoMensagem()" ></textarea>
	   <label id="QtChar"> </label>
	 <body>
</html>

来源：https://stackoverflow.com/questions/5533053/textarea-character-limit

标签

javascript

html

textarea

cross-browser