基于js原生和ajax的get和post方法以及jsonp的原生写法实例

<div class="jb51code">
<pre class="brush:xhtml;">
login.onclick = function(){
var xhr = new XMLHttpRequest();
xhr.open("get","http://localhost/ajax2/test2.php?username="+username.value+"&pwd="+pwd2.value,true);
xhr.send();
xhr.onreadystatechange = function(){
if (xhr.readyState == 4) {
if (xhr.status>=200 && xhr.status<300) {
alert(xhr.responseText);
};
};
}
}