Enter键禁止表单提交

Enter键禁止表单提交js代码:

             //禁用Enter键表单自动提交
             document.onkeydown = function (event) {
                 var target, code, tag;
                 if (!event) {
                     event = window.event; //针对ie浏览器
                     target = event.srcElement;
                     code = event.keyCode;
                     if (code == ) {
                         return false;
                     }
                 }
                 else {
                     target = event.target; //针对遵循w3c标准的浏览器，如Firefox
                     code = event.keyCode;
                     if (code == ) {
                         return false;
                     }
                 }
             };