如何限制用户在文本区域只输入250个单词？

Question

我创建了一个表单供用户提交摘要.但在提交时我需要检查天气他们已经添加了超过250个单词.我只需要250个单词.这该怎么做 ？

我尝试了一些JavaScript,但它仅适用于250个字符.

这是我的代码

function maxlength(element, maxvalue)
   {
  var q = eval("document.upload."+element+".value.length");
   var r = q - maxvalue;
   var msg = "Sorry, you have input "+q+" characters into the "+
  "text area box you just completed. It can return no more than "+
  maxvalue+" words to be processed. Please abbreviate "+
 "your text by at least "+r+" words";
    if (q > maxvalue) alert(msg);
      }

我的textarea是:

  <tr>
   <td><label>Abstract Details</label> </td>
 <td><label>Please enter data, at most 250 words:</label>
  <br/><textarea rows="6" cols="80"name="box_name"   onChange="maxlength('box_name', 250)" style="width: 257px; height: 131px;">    </textarea></td>
    </tr>
  <tr>

如何限制250个单词.

提前致谢

Answer 1

要防止在textarea中超过250个字符时提交表单,请添加id="box_id"到textarea并将此事件添加到表单元素:

onsubmit="return maxlength(getElementById('box_id'), 250);

现在在您的函数中将此值拆分多个空格:

function maxlength(element, maxvalue){
    var q = element.value.split(/[\s]+/).length;
    if(q > maxvalue){
        var r = q - maxvalue;
        alert("Sorry, you have input "+q+" words into the "+
        "text area box you just completed. It can return no more than "+
        maxvalue+" words to be processed. Please abbreviate "+
        "your text by at least "+r+" words");
        return false;
    }
}

要利用新的HTML属性,您还可以将"pattern"属性添加到textarea,并将正则表达式限制输入设置为250个单词:

<textarea rows="6" cols="80"name="box_name"   onChange="maxlength(this, 250)" style="width: 257px; height: 131px;" 
    pattern="^(?:\b\w+\b[\s\r\n]*){1,250}$">
</textarea>

这个正则表达式模式来自以下SO线程,它接触250个单词的类似问题:使用正则表达式限制响应中的单词数