如何发送POST和GET请求？

var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
    if (xhr.readyState == 4 && xhr.status == 200) {
        console.log(xhr.responseText);
    }
};
xhr.open("GET", "https://example.com/api/data?param1=value1&param2=value2", true);
xhr.send();

var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function() {
    if (xhr.readyState == 4 && xhr.status == 200) {
        console.log(xhr.responseText);
    }
};
xhr.open("POST", "https://example.com/api/data", true);
xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xhr.send("param1=value1&param2=value2");