I have this function to access the DeepL API

    function translator(inputText){
    var url = "https://api-free.deepl.com/v2/translate";

    var xhr = new XMLHttpRequest();
    xhr.open("POST", url);
    xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
    xhr.onreadystatechange = function () {
    if (xhr.readyState === 4) {
        console.log(xhr.status);
        console.log(xhr.responseText);
        
    }
    };

    var data = "auth_key=123456x&text="+inputText+"&target_lang=EN";

    xhr.send(data);
}

and I would like to store the response that comes back as a string. How to do this?