如何报告用户输入的字符串长度

好的，这是我的脚本...不过，我无法让它输出字符串的长度！请帮忙，在Javascript方面，我是一个完全的菜鸟，这是大学课程。谢谢！

<HTML>
<HEAD>
<TITLE></TITLE>
<script type="text/javascript">
/*
Purpose of script: report length of string given by user
*/
  "use strict";
  function stringLength()
  {
  var str=(document.StringLength.string);
  var n=str.length;
  document.StringLength.answerBox.value=length;
  }
  //Get string from user
  //Output to user
  </script>
</HEAD>
<BODY>
<form name = StringLength>
Enter Your String <input type = "text" name = "string">
<br>
Length <input type = "text" name = "answerBox">
<input type = "button" onclick = "stringLength()" value = "Run">

  </BODY>
</HTML>

您需要

检查string输入框值的长度

function stringLength(){
    var str=document.StringLength.string.value;
    var len=str.length;
    document.StringLength.answerBox.value=len;
}

请参阅此 JSFiddle 以获取演示。

你可以这样尝试：

var x = document.getElementById('yourinput');
var y = document.getElementById('characters');
x.onkeyup = function() {
  y.innerHTML = x.value.length;
}

吉斯菲德尔

function stringLength()
  {
  var str=(document.StringLength.string);
  var n=str.length;
  document.StringLength.answerBox.value = n ;
  }

你能试试这个吗，你还没有正确结束form标签

<HTML>
<HEAD>
<TITLE></TITLE>
<script type="text/javascript">
    /*
    Purpose of script: report length of string given by user
    */
      function stringLength()
      {          
          document.StringLength.answerBox.value=document.StringLength.string.value.length;
      }
  //Get string from user
  //Output to user
  </script>
</HEAD>
    <BODY>
        <form name ="StringLength" >
            Enter Your String <input type = "text" name = "string">
            <br>        Length <input type = "text" name = "answerBox">     
            <input type = "button" onclick = "stringLength()" value = "Run">
        </form>/*encloded form tag here*/
     </BODY>
</HTML>

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