Add support for download function in web

dio/lib/src/adapters/browser_adapter.dart

@@ -40,7 +40,7 @@ class BrowserHttpClientAdapter implements HttpClientAdapter {
     xhrs.add(xhr);
     xhr
       ..open(options.method, '${options.uri}')
-      ..responseType = 'arraybuffer';
+      ..responseType = options.blobUrl ? 'blob' : 'arraybuffer';
 
     final withCredentialsOption = options.extra['withCredentials'];
     if (withCredentialsOption != null) {
@@ -67,18 +67,34 @@ class BrowserHttpClientAdapter implements HttpClientAdapter {
     final completer = Completer<ResponseBody>();
 
     xhr.onLoad.first.then((_) {
-      final Uint8List body = (xhr.response as ByteBuffer).asUint8List();
-      completer.complete(
-        ResponseBody.fromBytes(
-          body,
-          xhr.status!,
-          headers: xhr.responseHeaders.map((k, v) => MapEntry(k, v.split(','))),
-          statusMessage: xhr.statusText,
-          isRedirect: xhr.status == 302 ||
-              xhr.status == 301 ||
-              options.uri.toString() != xhr.responseUrl,
-        ),
-      );
+      if (options.blobUrl) {
+        completer.complete(
+          ResponseBody.fromString(
+            Url.createObjectUrl(xhr.response),
+            xhr.status!,
+            headers:
+                xhr.responseHeaders.map((k, v) => MapEntry(k, v.split(','))),
+            statusMessage: xhr.statusText,
+            isRedirect: xhr.status == 302 ||
+                xhr.status == 301 ||
+                options.uri.toString() != xhr.responseUrl,
+          ),
+        );
+      } else {
+        final Uint8List body = (xhr.response as ByteBuffer).asUint8List();
+        completer.complete(
+          ResponseBody.fromBytes(
+            body,
+            xhr.status!,
+            headers:
+                xhr.responseHeaders.map((k, v) => MapEntry(k, v.split(','))),
+            statusMessage: xhr.statusText,
+            isRedirect: xhr.status == 302 ||
+                xhr.status == 301 ||
+                options.uri.toString() != xhr.responseUrl,
+          ),
+        );
+      }
     });
 
     Timer? connectTimeoutTimer;

dio/lib/src/dio/dio_for_browser.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import '../adapters/browser_adapter.dart';
 import '../cancel_token.dart';
 import '../dio.dart';
@@ -29,9 +31,24 @@ class DioForBrowser with DioMixin implements Dio {
     String lengthHeader = Headers.contentLengthHeader,
     Object? data,
     Options? options,
-  }) {
-    throw UnsupportedError(
-      'The download method is not available in the Web environment.',
+  }) async {
+    final Response response = await fetch(
+      RequestOptions(
+        baseUrl: urlPath,
+        data: data,
+        method: 'GET',
+        queryParameters: queryParameters,
+        cancelToken: cancelToken,
+        onReceiveProgress: onReceiveProgress,
+        blobUrl: true,
+      ),
     );
+
+    final completer = Completer<Response>();
+
+    // Set response in Completer
+    completer.complete(response);
+
+    return DioMixin.listenCancelForAsyncTask(cancelToken, completer.future);
   }
 }

dio/lib/src/options.dart

@@ -485,6 +485,7 @@ class RequestOptions extends _RequestConfig with OptionsMixin {
     this.onReceiveProgress,
     this.onSendProgress,
     this.cancelToken,
+    this.blobUrl = false,
     super.method,
     super.sendTimeout,
     super.receiveTimeout,
@@ -526,6 +527,7 @@ class RequestOptions extends _RequestConfig with OptionsMixin {
     ProgressCallback? onReceiveProgress,
     ProgressCallback? onSendProgress,
     CancelToken? cancelToken,
+    bool? blobUrl,
     Map<String, dynamic>? extra,
     Map<String, dynamic>? headers,
     bool? preserveHeaderCase,
@@ -558,6 +560,7 @@ class RequestOptions extends _RequestConfig with OptionsMixin {
       connectTimeout: connectTimeout ?? this.connectTimeout,
       data: data ?? this.data,
       path: path ?? this.path,
+      blobUrl: blobUrl ?? false,
       baseUrl: baseUrl ?? this.baseUrl,
       queryParameters: queryParameters ?? Map.from(this.queryParameters),
       onReceiveProgress: onReceiveProgress ?? this.onReceiveProgress,
@@ -630,6 +633,11 @@ class RequestOptions extends _RequestConfig with OptionsMixin {
 
   /// {@macro dio.options.ProgressCallback}
   ProgressCallback? onSendProgress;
+
+  /// Get blob url
+  ///
+  /// Only work in web
+  bool blobUrl;
 }
 
 bool _defaultValidateStatus(int? status) {