<input name="username" type="text" onkeyup="value=this.value.replace(/\D+/g,'')">

<input name="username" type="text" style="ime-mode:disabled">
<input name="username" type="text" onkeyup="value=value.replace(/[^\w\.\/]/ig,'')">

<input name="username" type="text" onkeyup="value=value.replace(/[^\w=@#]|_/ig,'')">

<input name="name" type="text" value="只录入大写字母和数字" style="color:gray" onfocus="this.value='';this.style.color='black'" onkeyup="this.value=this.value.replace(/[^A-Z0-9]/gi,'');this.value=this.value.toLocaleUpperCase();

<input name="username" type="text" onkeyup="value=value.replace(/[^\u4E00-\u9FA5]/g,'')">

TextField.restrict = "此处为可输入的内容";
field.restrict = "^此处为禁止输入的内容";

field.restrict = "a-zA-z"; //只允许大小字母
field.restrict = "a-zA-z "; //只允许字母和空格
field.restrict = "0-9"; //只允许数字
field.restrict = "^abcdefg"; //除了小写字母abcdefg不允许外,其它都允许
field.restrict = "^a-z"; //所有小写字母都不允许,但是,其它内容都允许,包括大写字母
field.restrict = "0-9^5"; //只允许数字,但5例外

field.restrict = "0-9\\-"; //允许数字和破折号
field.restrict = "0-9\\^"; //允许数字和^
field.restrict = "0-9\\\\"; //允许数字和反斜杠

field.restrict = "^\u001A";