JS文本框不能输入空格验证方法

<input type="text" onkeyup="this.value=this.value.replace(/^ +| +$/g,'')">

 <input type="text" onkeyup="this.value=this.value.replace(/[, ]/g,'')">

<script type="text/javascript">
        function myfunction() {
            var a = $("text1").val();
            if ($.trim(a) == "") {
                alert("不能为空！");
                return false;
            }
        }
    </script>