禁用Enter键表单自动提交实现代码

//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 == 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; } 
} 
} 
};