使用Javascript计算并显示文本框中的字符数

问题描述

我正在从事一个项目，该项目需要我计算在文本框中输入的字符数，并在页面的其他位置动态显示结果.

I am working on a project that requires me to count the number of characters entered in a text box and dynamically display the result elsewhere on the page.

正如我所说，这最好用 jQuery 或 Javascript 来完成.

As I said, this would preferably be done in jQuery or Javascript.

提前致谢.

推荐答案

我想分享我在项目中使用的答案，它运行良好.

I would like to share my answer which i used in my project and it is working fine.

<asp:TextBox ID="txtComments" runat="server" TextMode="MultiLine" Rows="4" Columns="50" placeholder="Maximum limit: 100 characters"></asp:TextBox><br />
<span id="spnCharLeft"></span>

<script type='text/javascript'>
    $('#spnCharLeft').css('display', 'none');
    var maxLimit = 100;
    $(document).ready(function () {
        $('#<%= txtComments.ClientID %>').keyup(function () {
            var lengthCount = this.value.length;              
            if (lengthCount > maxLimit) {
                this.value = this.value.substring(0, maxLimit);
                var charactersLeft = maxLimit - lengthCount + 1;                   
            }
            else {                   
                var charactersLeft = maxLimit - lengthCount;                   
            }
            $('#spnCharLeft').css('display', 'block');
            $('#spnCharLeft').text(charactersLeft + ' Characters left');
        });
    });
</script>

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