console 命令行工具 X clear

console

 var oTxt = document.querySelector('#txt-num');
        oTxt.onkeydown = function (ev) {
            var oEvent = ev || event;
            if (oEvent.keyCode < 48 || oEvent.keyCode > 57)             {
                return false;
            }
        };

<input type="text" id="txt-num" />