var body= document.body;
//创建链接
function createa(url,text)
{
    var a = document.createElement("a");
    a.href = url;
    a.innerHTML = text;
    a.style.color = "red";
    body.appendChild(a);
}
// 调用函数创建链接
createa("http://www.imooc.com/","慕课网");