js代码：

/*获取光标位置*/function getCursorPos(obj){var CaretPos = 0;// IE Supportif (document.selection) {obj.focus (); //获取光标位置函数var Sel = document.selection.createRange ();Sel.moveStart ('character', -obj.value.length);CaretPos = Sel.text.length;}// Firefox/Safari/Chrome/Opera supportelse if (obj.selectionStart || obj.selectionStart == '0')CaretPos = obj.selectionEnd;return (CaretPos);}/*定位光标*/function setCursorPos(obj,pos){if(obj.setSelectionRange) { //Firefox/Safari/Chrome/Operaobj.focus(); //obj.setSelectionRange(pos,pos);} else if (obj.createTextRange) { // IEvar range = obj.createTextRange();range.collapse(true);range.moveEnd('character', pos);range.moveStart('character', pos);range.select();}}/*替换后定位光标在原处,可以这样调用οnkeyup=replaceAndSetPos(this,/[^/d]/g,'');*/function replaceAndSetPos(obj,pattern,text){/*if(event.shiftKey||event.altKey||event.ctrlKey||event.keyCode==16||event.keyCode==17||event.keyCode==18||(event.shiftKey&&event.keyCode==36))return; */var pos=getCursorPos(obj);//保存原始光标位置var temp=obj.value; //保存原始值obj.value=temp.replace(pattern,text);//替换掉非法值//截掉超过长度限制的字串（此方法要求已设定元素的maxlength属性值）var max_length = obj.getAttribute? parseInt(obj.getAttribute("maxlength")) : "";if( obj.value.length > max_length){//法一：obj.value = obj.value.substring( 0,max_length);若用户在中间进行输入，此方法则达不到效果//法二：可以满足任何情况（当超过输入了，去掉新输入的字符）var str1 = obj.value.substring( 0,pos-1 );var str2 = obj.value.substring( pos,max_length+1 );obj.value = str1 + str2;/*法三：在支持keycode等一系列的情况下使用var e=e||event;currKey=e.keyCode||e.which||e.charCode;currKey = 0;或window.οnkeydοwn=function(){if( event.keyCode!=37 && event.keyCode!=39 && event.keyCode!=8 )// 左、右、删除{ return false; }}*/}pos=pos-(temp.length-obj.value.length);//当前光标位置setCursorPos(obj,pos);//设置光标}

html代码：

<input class="form-control" id="name" name="" type="text" οnkeyup="replaceAndSetPos(this,/[^\a-\z\A-\Z0-9]/g,'')" οninput="replaceAndSetPos(this,/[^\a-\z\A-\Z0-9]/g,'')" maxlength="16" placeholder="字母、数字"/>