https://blog.youkuaiyun.com/third_week/article/details/80279537
输入大小写字母、数字、下划线:
<input type="text" οnkeyup="this.value=this.value.replace(/[^\w_]/g,'');">
输入小写字母、数字、下划线:
<input type="text" οnkeyup="this.value=this.value.replace(/[^a-z0-9_]/g,'');">
输入数字和点
<input type="text" οnkeyup="value=value.replace(/[^\d.]/g,'')">
输入中文:
<input type=“text” οnkeyup=“this.value=this.value.replace(/[^\u4e00-\u9fa5]/g,’’)”>
输入数字:
<input type="text" οnkeyup="this.value=thi