只能输入数字<input type="text" rel="int" onblur="check(this)"/><br/>
只能输入电子邮件<input type="text" rel="email" onblur="check(this)"/>

<script>

function check(obj){
    var result;
    switch(obj.getAttribute("rel")){
        case "int":
            result = /^\d+$/.test(obj.value);
            break;
        case "email":
            result = /^\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$/.test(obj.value);
            break;
        default:
            break;
    }
    if(!(result)){
        obj.value = "";
    }
}
</script>