21.ajax使用post请求

ajax使用post请求时

1.将请求方式改为post
2.设置请求头
3.设置请求体

示例代码:

function checkaccount() {
    //获取到username节点对象
    var username = document.getElementById("un");
    
    //ajax
    var ajax = new XMLHttpRequest();
    
    //open
    ajax.open("post","/checkaccount.do",true);
    
    //注册监听
    var sp = document.getElementById("sp");
    ajax.onreadystatechange = function() {
        if (ajax.readyState == 4 && ajax.status == 200) {
            sp.innerHTML = ajax.responseText;
        }else {
            sp.innerHTML = "网络有问题";
        }
    };
    
    //设置请求头
    ajax.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset=utf-8");
    
    //拼接参数(设置请求体,多个参数之间使用&分隔)
    var param = "username="+username.value;
    
    //发送请求
    ajax.send(param);
}