[ReactNative] Allow uploading native files (e.g. photos) and FormData via XMLHttpRequest

Libraries/Network/FormData.js

@@ -0,0 +1,67 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule FormData
+ * @flow
+ */
+'use strict';
+
+type FormDataValue = any;
+type FormDataPart = [string, FormDataValue];
+
+/**
+ * Polyfill for XMLHttpRequest2 FormData API, allowing multipart POST requests
+ * with mixed data (string, native files) to be submitted via XMLHttpRequest.
+ */
+class FormData {
+  _parts: Array<FormDataPart>;
+  _partsByKey: {[key: string]: FormDataPart};
+
+  constructor() {
+    this._parts = [];
+    this._partsByKey = {};
+  }
+
+  append(key: string, value: FormDataValue) {
+    var parts = this._partsByKey[key];
+    if (parts) {
+      // It's a bit unclear what the behaviour should be in this case.
+      // The XMLHttpRequest spec doesn't specify it, while MDN says that
+      // the any new values should appended to existing values. We're not
+      // doing that for now -- it's tedious and doesn't seem worth the effort.
+      parts[1] = value;
+      return;
+    }
+    parts = [key, value];
+    this._parts.push(parts);
+    this._partsByKey[key] = parts;
+  }
+
+  getParts(): Array<FormDataValue> {
+    return this._parts.map(([name, value]) => {
+      if (typeof value === 'string') {
+        return {
+          string: value,
+          headers: {
+            'content-disposition': 'form-data; name="' + name + '"',
+          },
+        };
+      }
+      var contentDisposition = 'form-data; name="' + name + '"';
+      if (typeof value.name === 'string') {
+        contentDisposition += '; filename="' + value.name + '"';
+      }
+      return {
+        ...value,
+        headers: {'content-disposition': contentDisposition},
+      };
+    });
+  }
+}
+
+module.exports = FormData;