Question

我正在尝试解决一个需要我在javascript中使用charAt的问题。简单问题，让我构建一个表单，使用户能够输入几行文本，然后使用String和charAt搜索字符，以确定搜索字符的出现次数。结果将显示在文本区域中。如果在搜索中找不到该字符，则使用window.open方法在新窗口中显示，并进行如下按钮：“在文本字符串中找不到搜索字符！”

我想出了以下代码，但实际上并没有用，我对出了什么问题感到有些困惑！

<!-- begin snippet: js hide: false console: true babel: false -->

<!DOCTYPE html>
<html lang="en">

<head>
<meta charset="utf-8">
<title>search using string method</title>

</head>

<body onload="document.getElementById('key').focus();">

<section class="body">
        <h3>Object Exercise Solution 3 - charAt() - Mary had a little lamb</h3>

      <form name="myForm">
         
         <p>Enter a character to search for
            <textarea name="key" rows="3" cols="60" autofocus>
</textarea><br><br>   
<input type="button" value="Go" onclick="search();">
<input type="reset" value="Reset" onclick="document.forms['myForm'].elements['key'].focus();">
</p>
         <br><br>
         
<h3>Occurrences of each digit entered above:</h3>
<textarea name="output" rows="14" cols="23" readonly></textarea>
      </form>
</section>
</body>
</html>

<script>

function search()
         {
            var count=0;

            var key = document.getElementById("key").value.toLowerCase().charAt(0);
             var key = key.toLowerCase();

            var stringToSearch=["a","b","c","d","e","f","g","h","i","j","k","l","m","n",
            "o","p","q","r","s","t","u","v","w","x","y","z"];
            var stringToSearch=stringToSearch.toLowerCase(); 


             for (i=0; i < stringToSearch.length; i++)
                     {

                    if (stringToSearch.charAt(i) == key)
                             count++;     
                     }         

            if ( count == 0 )
               document.getElementById("output").value=key + " not found";
            else
               document.getElementById("output").value=count + 
                  " occurrence(s) of " + key + " found";
         }
</script>

这是我第一次写一个问题“堆栈溢出”我希望我清楚并使用正确的格式！如果你能提供帮助，请告诉我！

Answer 1

首先：我添加了id ="key"

<textarea id ="key" name="key" rows="3" cols="60" autofocus>
</textarea><br><br>

当您使用document.getElementById('key').focus()时，代码将尝试查找id未使用html定义的元素。

此外，document.getElementById("output").value将找不到任何元素，因为id不存在的元素。所以，改变了以下内容：

<textarea id = "output" name="output" rows="14" cols="23" readonly></textarea>

第二：搜索功能未正确更新，请检查更新后的搜索功能。此外，我将一些代码作为注释，因为它不能用作代码段，取消注释要使用的代码段。

下面给出了工作代码段：

＆＃13;

<!DOCTYPE html>
<html lang="en">

<head>
<meta charset="utf-8">
<title>search using string method</title>

</head>
<script>function search()
         {
            var count={};

            var key = document.getElementById("key").value.toLowerCase();
             var key = key.toLowerCase();

            var stringToSearch=["a","b","c","d","e","f","g","h","i","j","k","l","m","n",
            "o","p","q","r","s","t","u","v","w","x","y","z"];
            var stringToSearch=stringToSearch.join('').toLowerCase(); 

           for(var j = 0; j < key.length;j++) {
            var checkChr = key[j];
             for (i=0; i < stringToSearch.length; i++)
                     {
                    if(!count[stringToSearch.charAt(i)]) {
                      count[stringToSearch.charAt(i)] = 0;
                    }
                    if (stringToSearch.charAt(i) == checkChr)
                             count[stringToSearch.charAt(i)]++;     
                     }
             }

            for (i = 0; i < stringToSearch.length; i++)
            if ( count[stringToSearch.charAt(i)] == 0 )
               document.getElementById("output").value= document.getElementById("output").value + stringToSearch.charAt(i) + " not found\n";
            else
               document.getElementById("output").value=document.getElementById("output").value + count[stringToSearch.charAt(i)] + 
                  " occurrence(s) of " + stringToSearch.charAt(i) + " found\n";
                  alert(document.getElementById("output").value);

//Use the commented line in your real code.
                  //var myWindow = window.open("", "MsgWindow", "width=200,height=100");
    //myWindow.document.write(document.getElementById("output").value);
         }</script>
<body onload="document.getElementById('key').focus();">

<section class="body">
        <h3>Object Exercise Solution 3 - charAt() - Mary had a little lamb</h3>

      <form name="myForm">
         
         <p>Enter a character to search for
            <textarea id ="key" name="key" rows="3" cols="60" autofocus>
</textarea><br><br>   
<input type="button" value="Go" onclick="search();">
<input type="reset" value="Reset" onclick="document.forms['myForm'].elements['key'].focus();">
</p>
<br><br>
         
<h3>Occurrences of each digit entered above:</h3>
<textarea id = "output" name="output" rows="14" cols="23" readonly></textarea>
      </form>
</section>
</body>
</html>

＆＃13;

使用字符串方法charAt（）在javascript

1 个答案: