added PDF Merger

static/js/api_handler.js

@@ -0,0 +1,53 @@
+function downloadURI(uri, name) {
+    var link = document.createElement("a");
+    link.download = name;
+    link.href = uri;
+    document.body.appendChild(link);
+    link.click();
+    document.body.removeChild(link);
+    delete link;
+}
+
+function uploadPDF_split() {
+    const fileInput = document.getElementById('split_pdfFile');
+    const file = fileInput.files[0];
+    const formData = new FormData();
+    formData.append('pdf', file);
+
+    const backendURL = '/split_to_zip';
+
+    fetch(backendURL, {
+        method: 'POST',
+        body: formData
+    })
+    .then(response => response.json())
+    .then(data => {
+        console.debug("data from Backend: ", data)
+        downloadURI(data["url"], data["name"]);
+    })
+    .catch(error => console.error(error));
+}
+
+
+function uploadPDF_merge() {
+    const fileInput_1 = document.getElementById('merge_pdfFile_1');
+    const file_1 = fileInput_1.files[0];
+    const fileInput_2 = document.getElementById('merge_pdfFile_2');
+    const file_2 = fileInput_2.files[0];
+    const formData = new FormData();
+    formData.append('pdf_1', file_1);
+    formData.append('pdf_2', file_2);
+
+    const backendURL = '/merge_to_pdf';
+
+    fetch(backendURL, {
+        method: 'POST',
+        body: formData
+    })
+    .then(response => response.json())
+    .then(data => {
+        console.debug("data from Backend: ", data)
+        downloadURI(data["url"], data["name"]);
+    })
+    .catch(error => console.error(error));
+}