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 == 13) { 
                    tag = target.tagName; 
                    if (tag == "TEXTAREA") { return true; } 
                    else { return false; } 
                } 
            } 
            else { 
                target = event.target; //针对遵循w3c标准的浏览器，如Firefox 
                code = event.keyCode; 
                if (code == 13) { 
                    tag = target.tagName; 
                    if (tag == "INPUT") { return false; } 
                    else { return true; }  
                } 
            }  
 }