XHR Download file

xhrdl.js

        $("#saveAndDownload").click(function() {
            var invoiceData = getJsonData();
            var xhr = new XMLHttpRequest();
            xhr.open('PUT', 'SOME_URL', true);
            xhr.responseType = 'arraybuffer';
            xhr.setRequestHeader('X-CSRFToken', getCookie('csrftoken'));
            xhr.send(JSON.stringify(invoiceData));
            xhr.onload = function(e) {
                var arr = new Uint8Array(this.response);
                var raw = String.fromCharCode.apply(null,arr);
                var b64 = btoa(raw);
                var filename = this.getResponseHeader('Content-Disposition').split('attachment; filename=')[1]

                var element = document.createElement('a');
                element.setAttribute('href', 'data:application/pdf;base64,' + b64);
                element.setAttribute('download', filename);

                element.style.display = 'none';
                document.body.appendChild(element);

                element.click();

                document.body.removeChild(element);
            };
        });