blocks|key|4605323|text|你只在document.ready上禁用，当DOM准备就绪时，这只会发生一次，但当textbox为空时，你也需要在keyup事件中使用disable。还要将$(this).val.length更改为$(this).val().length|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4605324|$(document).ready(function(){
++++$('.sendButton').attr('disabled',true);
++++$('#message').keyup(function(){
++++++++if($(this).val().length+!=0)
++++++++++++$('.sendButton').attr('disabled',+false);++++++++++++
++++++++else
++++++++++++$('.sendButton').attr('disabled',true);
++++})
});|code-block|syntax|javascript|4605325|或者，您可以使用条件运算符而不是if语句。也可以使用属性代替attr，因为对于disabled、checked等属性，属性不是recommended+by+jQuery+1.6或更高。|BOLD|4605326|对于jQuery+1.6，对于尚未设置的属性，.attr()方法将返回|4605327|。要检索和更改DOM属性，如表单元素的选中、选中或禁用状态，请使用.prop()方法jQuery+docs|blockquote|4605328|4605329|4605330|$(document).ready(function(){
++++$('.sendButton').prop('disabled',true);
++++$('#message').keyup(function(){
++++++++$('.sendButton').prop('disabled',+this.value+==+""+?+true+:+false);+++++
++++})
});++|4605331|entityMap|0|LINK|mutability|MUTABLE|url|http://api.jquery.com/attr/|1|http://api.jquery.com/prop/|2^0|3|E|M|3|1V|7|26|I|2R|K|0|0|Q|8|1R|P|0|0|0|X|7|1|16|B|2|0|0|0|0^^$0|@$1|2|3|4|5|6|7|17|8|@$9|18|A|19|B|C]|$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]|$9|1G|A|1H|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|1I|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1J|8|@$9|1K|A|1L|B|M]]|D|@$9|1M|A|1N|1|1O]]|E|$]]|$1|N|3|O|5|6|7|1P|8|@]|D|@]|E|$]]|$1|P|3|Q|5|R|7|1Q|8|@]|D|@$9|1R|A|1S|1|1T]|$9|1U|A|1V|1|1W]]|E|$]]|$1|S|3|-4|5|6|7|1X|8|@]|D|@]|E|$]]|$1|T|3|-4|5|6|7|1Y|8|@]|D|@]|E|$]]|$1|U|3|V|5|H|7|1Z|8|@]|D|@]|E|$I|J]]|$1|W|3|-4|5|6|7|20|8|@]|D|@]|E|$]]]|X|$Y|$5|Z|10|11|E|$12|13]]|14|$5|Z|10|11|E|$12|15]]|16|$5|Z|10|11|E|$12|13]]]]

<p>You are disabling only on <code>document.ready</code> and this happens only once when <code>DOM</code> is ready but you need to <code>disable</code> in keyup event too when textbox gets empty. Also change <code>$(this).val.length</code> to <code>$(this).val().length</code></p>

<pre><code>$(document).ready(function(){
    $('.sendButton').attr('disabled',true);
    $('#message').keyup(function(){
        if($(this).val().length !=0)
            $('.sendButton').attr('disabled', false);            
        else
            $('.sendButton').attr('disabled',true);
    })
});
</code></pre>

<p>Or you can use conditional operator instead of if statement. also use <strong>prop instead of attr</strong> as attribute is not <a href="http://api.jquery.com/attr/">recommended by jQuery 1.6</a> and above for disabled, checked etc.</p>

<blockquote>
  <p>As of jQuery 1.6, the .attr() method returns undefined for attributes
  that have not been set. To retrieve and change DOM properties such as
  the checked, selected, or disabled state of form elements, use the
  <a href="http://api.jquery.com/prop/">.prop()</a> method, <a href="http://api.jquery.com/attr/">jQuery docs</a></p>
</blockquote>

<pre><code>$(document).ready(function(){
    $('.sendButton').prop('disabled',true);
    $('#message').keyup(function(){
        $('.sendButton').prop('disabled', this.value == "" ? true : false);     
    })
});  
</code></pre>


blocks|key|920793|text|试试这段代码|type|unstyled|depth|inlineStyleRanges|entityRanges|data|920794|$(document).ready(function(){
++++$('.sendButton').attr('disabled',true);

++++$('#message').keyup(function(){
++++++++if($(this).val().length+!=0){
++++++++++++$('.sendButton').attr('disabled',+false);
++++++++}
++++++++else
++++++++{
++++++++++++$('.sendButton').attr('disabled',+true);++++++++
++++++++}
++++})
});|code-block|syntax|javascript|920795|检查demo+Fiddle|offset|length|920796|您缺少if语句的else部分(如果textbox为空，则再次禁用该按钮)和if($(this).val.length+!=0){中val函数后的圆括号()|style|CODE|920797|entityMap|0|LINK|mutability|MUTABLE|url|http://jsfiddle.net/nh8Xw/^0|0|0|2|B|0|0|11|R|1T|3|23|2|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@]|9|@$I|Z|J|10|1|11]]|A|$]]|$1|K|3|L|5|6|7|12|8|@$I|13|J|14|M|N]|$I|15|J|16|M|N]|$I|17|J|18|M|N]]|9|@]|A|$]]|$1|O|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

<p>Try this code</p>

<pre><code>$(document).ready(function(){
    $('.sendButton').attr('disabled',true);

    $('#message').keyup(function(){
        if($(this).val().length !=0){
            $('.sendButton').attr('disabled', false);
        }
        else
        {
            $('.sendButton').attr('disabled', true);        
        }
    })
});
</code></pre>

<p>Check <a href="http://jsfiddle.net/nh8Xw/" rel="noreferrer">demo Fiddle</a></p>

<p>You are missing the else part of the if statement (to disable the button again if textbox is empty) and parentheses <code>()</code> after <code>val</code> function in  <code>if($(this).val.length !=0){</code></p>


blocks|key|924259|text|请试试这个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|924260|<!DOCTYPE+html>
<html>
++<head>
++++<title>Jquery</title>
++++<meta+charset="utf-8">+++++++
++++<script+src='http://code.jquery.com/jquery-1.7.1.min.js'></script>
++</head>

++<body>

++++<input+type="text"+id="message"+value=""+/>
++++<input+type="button"+id="sendButton"+value="Send">

++++<script>
++++$(document).ready(function(){++

++++++var+checkField;

++++++//checking+the+length+of+the+value+of+message+and+assigning+to+a+variable(checkField)+on+load
++++++checkField+=+$("input#message").val().length;++

++++++var+enableDisableButton+=+function(){+++++++++
++++++++if(checkField+>+0){
++++++++++$('#sendButton').removeAttr("disabled");
++++++++}+
++++++++else+{
++++++++++$('#sendButton').attr("disabled","disabled");
++++++++}
++++++}++++++++

++++++//calling+enableDisableButton()+function+on+load
++++++enableDisableButton();++++++++++++

++++++$('input#message').keyup(function(){+
++++++++//checking+the+length+of+the+value+of+message+and+assigning+to+the+variable(checkField)+on+keyup
++++++++checkField+=+$("input#message").val().length;
++++++++//calling+enableDisableButton()+function+on+keyup
++++++++enableDisableButton();
++++++});
++++});
++++</script>
++</body>
</html>|code-block|syntax|javascript|924261|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>Please try this</p>

<pre><code>&lt;!DOCTYPE html&gt;
&lt;html&gt;
  &lt;head&gt;
    &lt;title&gt;Jquery&lt;/title&gt;
    &lt;meta charset="utf-8"&gt;       
    &lt;script src='http://code.jquery.com/jquery-1.7.1.min.js'&gt;&lt;/script&gt;
  &lt;/head&gt;

  &lt;body&gt;

    &lt;input type="text" id="message" value="" /&gt;
    &lt;input type="button" id="sendButton" value="Send"&gt;

    &lt;script&gt;
    $(document).ready(function(){  

      var checkField;

      //checking the length of the value of message and assigning to a variable(checkField) on load
      checkField = $("input#message").val().length;  

      var enableDisableButton = function(){         
        if(checkField &gt; 0){
          $('#sendButton').removeAttr("disabled");
        } 
        else {
          $('#sendButton').attr("disabled","disabled");
        }
      }        

      //calling enableDisableButton() function on load
      enableDisableButton();            

      $('input#message').keyup(function(){ 
        //checking the length of the value of message and assigning to the variable(checkField) on keyup
        checkField = $("input#message").val().length;
        //calling enableDisableButton() function on keyup
        enableDisableButton();
      });
    });
    &lt;/script&gt;
  &lt;/body&gt;
&lt;/html&gt;
</code></pre>


blocks|key|4605475|text|一种简单的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4605476|function+toggleButton(ref,bttnID){
++++document.getElementById(bttnID).disabled=+((ref.value+!==+ref.defaultValue)+?+false+:+true);
}


<input+...+onkeyup="toggleButton(this,'bttnsubmit');">
<input+...+disabled='disabled'+id='bttnsubmit'+...+>|code-block|syntax|javascript|4605477|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>An easy way to do:</p>

<pre><code>function toggleButton(ref,bttnID){
    document.getElementById(bttnID).disabled= ((ref.value !== ref.defaultValue) ? false : true);
}


&lt;input ... onkeyup="toggleButton(this,'bttnsubmit');"&gt;
&lt;input ... disabled='disabled' id='bttnsubmit' ... &gt;
</code></pre>


blocks|key|2061432|text|对于那些使用coffeescript的人，我已经将我们在全球使用的代码放在最广泛使用的表单上禁用提交按钮。改编自Adil上面的答案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2061433|$('#new_post+button').prop+'disabled',+true
$('#new_post+#post_message').keyup+->
++++$('#new_post+button').prop+'disabled',+if+@value+==+''+then+true+else+false
++++return|code-block|syntax|javascript|2061434|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

<p>For those that use <em>coffeescript</em>, I've put the code we use globally to disable the submit buttons on our most widely used form. An adaption of Adil's answer above. </p>

<pre><code>$('#new_post button').prop 'disabled', true
$('#new_post #post_message').keyup -&gt;
    $('#new_post button').prop 'disabled', if @value == '' then true else false
    return
</code></pre>


<p>I'm trying to disable submit button if the user hasn't provided any text. </p>

<p>At first sight it looks that everything works just fine, but if user types some text, then deletes it, the submit button becomes enabled. </p>

<p>Here is my code:</p>

<pre><code>$(document).ready(function(){
    $('.sendButton').attr('disabled',true);
    $('#message').keyup(function(){
        if($(this).val.length !=0){
            $('.sendButton').attr('disabled', false);
        }
    })
});
</code></pre>


If input field is empty, disable submit button

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

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如果用户没有提供任何文本，我正在尝试禁用提交按钮。乍一看，一切都很正常，但如果用户键入一些文本，然后将其删除，提交按钮就会启用。下面是我的代码：$(document).ready(function(){    $('.sendButton').attr('disabled',true);    $('#message'...

问如果输入字段为空，则禁用提交按钮
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问如果输入字段为空，则禁用提交按钮EN