function $(id) { return document.getElementById(id); } var maxLen=255; function checkMaxInput(){ if($("summary").value.length>maxLen){ $("summary").value=$("summary").value.substring(0,maxLen); }else{ $("leaves").innerHTML=maxLen-$("summary").value.length; } }
HTML部分:
<tr> <td>摘要:</td> <td> <html:textarea property="summary" rows="5" cols="60" onkeyup="checkMaxInput()"/> <br> 还可以输入<span>255</span>个字符 </td> </tr>
jQuery插件textlimit实现Javascript统计和限制字符个数功能
使用jQuery插件textlimit可以实现统计和限制字符个数功能,可应用于文本框与文本区域,当输入文字时textlimit插件会及时统计当前文本框与文本区域中的字符个数,如果达到限制数则不允许输入,同时可设置字符删除速度,
使用实例
一、包含文件部分
<script type="text/javascript" src="https://www.jb51.net/jquery.js"></script> <script type="text/javascript" src="https://www.jb51.net/textlimit.js"></script>
二、HTML部分
<input type="text" value="" /><span>20</span>/256
三、Javascript部分
<script type="text/javascript"> jQuery(document).ready(function(){ jQuery("#test").textlimit("span",256); }); </script>
当在ID为test的文本框中输入文字时,textlimit插件统计当前输入字符个数并显示在一个span的元素中,如上效果图,textlimit接口如下:
textlimit(counter_el, thelimit, speed)
接口参数说明:
counter_el表示显示当前统计个数的选择器标签,如:span
thelimit表示限制个数,也就是最多可输入的个数,如:256
speed表示删除字符速度,默认为15,注意,如果不需要可设置为-1,但不能是0
注意:英文字符与汉字字符都统计为一个字符
textlimit插件统计和限制字符数非常简单,具体大家可以看看textlimit的库文件,非常值得推荐。
/* * TextLimit - jQuery plugin for counting and limiting characters for input and textarea fields * * pass '-1' as speed if you don't want the char-deletion effect. (don't just put 0) * Example: jQuery("Textarea").textlimit('span.counter',256) * * $Version: 2009.07.25 +r2 * Copyright (c) 2009 Yair Even-Or * vsync.design@gmail.com */ (function(jQuery) { jQuery.fn.textlimit=function(counter_el, thelimit, speed) { var charDelSpeed = speed || 15; var toggleCharDel = speed != -1; var toggleTrim = true; var that = this[0]; var isCtrl = false; updateCounter(); function updateCounter(){ if(typeof that == "object") jQuery(counter_el).text(thelimit - that.value.length+" characters remaining"); }; this.keydown (function(e){ if(e.which == 17) isCtrl = true; var ctrl_a = (e.which == 65 && isCtrl == true) ? true : false; // detect and allow CTRL + A selects all. var ctrl_v = (e.which == 86 && isCtrl == true) ? true : false; // detect and allow CTRL + V paste. // 8 is 'backspace' and 46 is 'delete' if( this.value.length >= thelimit && e.which != '8' && e.which != '46' && ctrl_a == false && ctrl_v == false) e.preventDefault(); }) .keyup (function(e){ updateCounter(); if(e.which == 17) isCtrl=false; if( this.value.length >= thelimit && toggleTrim ){ if(toggleCharDel){ // first, trim the text a bit so the char trimming won't take forever // Also check if there are more than 10 extra chars, then trim. just in case. if ( (this.value.length - thelimit) > 10 ) that.value = that.value.substr(0,thelimit+100); var init = setInterval ( function(){ if( that.value.length <= thelimit ){ init = clearInterval(init); updateCounter() } else{ // deleting extra chars (one by one) that.value = that.value.substring(0,that.value.length-1); jQuery(counter_el).text('Trimming... '+(thelimit - that.value.length)); } } ,charDelSpeed ); } else this.value = that.value.substr(0,thelimit); } }); }; })(jQuery);
PS:这里再为大家推荐两款相关在线工具供大家参考:
更多关于JavaScript相关内容感兴趣的读者可查看本站专题:《JavaScript数学运算用法总结》、《JavaScript数据结构与算法技巧总结》、《JavaScript数组操作技巧总结》、《JavaScript事件相关操作与技巧大全》、《JavaScript操作DOM技巧总结》及《JavaScript字符与字符串操作技巧总结》