blocks|key|59273|text|试试这段代码|type|unstyled|depth|inlineStyleRanges|entityRanges|data|59274|$(document).ready(function(){
++++$('.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|59275|检查demo+Fiddle|offset|length|59276|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|59277|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|59282|text|请试试这个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|59283|<!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|59284|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|275781|text|一种简单的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|275782|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|275783|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>


<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

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
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