JS判断键盘是否按的回车键并触发指定按钮点击操作

        document.onkeydown = function (e) {            if (!e) e = window.event;            if ((e.keyCode || e.which) == 13) {                var obtnLogin = document.getElementById("submit_btn");   //submit_btn为按钮ID                obtnLogin.focus();            }        }