Download file (PDF) with AJAX.

ajax-download-file.js

function downloadFile() {
    var blob = "";

    var xhr = new XMLHttpRequest();

    xhr.onload = function(){
        if (this.status == 200) {
            blob = new Blob([xhr.response], { type: 'application/pdf' });

            var link = document.createElement('a');

            link.href = window.URL.createObjectURL(blob);
            link.download = "document.pdf";

            link.click();

            alert("Nice!");
        } else {
            alert("Error. Estatus " + this.status + ".");
        }
    };

    try {
        xhr.open('POST', 'myurl.php', true);

        xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");

        xhr.responseType = 'blob';
        
        xhr.send('parameter1=&parameter2=');
    } catch (e) {
        alert(e);
    }
}