统计字数的textarea
文本域限制字数并且超多的字数自动替换成空：

<script type="text/javascript">function checkTextArea(obj,maxWords){var limit = maxWords;var limittip = document.getElementById('limittip');var str = obj.value;var len = str.length;var reallen = 0;for(i=0;i<len;i++){if(str.charCodeAt(i)>255){reallen += 2;if(reallen > limit){reallen -= 2; obj.value = str.substr(0,i); break;}}else{reallen++;if(reallen > limit){reallen--;obj.value = str.substr(0,i);break;}}}limittip.innerHTML = limit - reallen;}</script>

原文参考地址：http://www.decimage.com/web/js-for-textarea-count-bytes.html