diff --git a/src/fs.js b/src/fs.js
index 34e5955f9..911ff3f11 100644
--- a/src/fs.js
+++ b/src/fs.js
@@ -173,6 +173,7 @@ function writeFile(path:string, data:string | Array<number>, encoding:?string):P
 
 function appendFile(path:string, data:string | Array<number>, encoding:?string):Promise {
   encoding = encoding || 'utf8'
+  console.log('fs append file', data, encoding)
   if(typeof path !== 'string')
     return Promise.reject('Invalid argument "path" ')
   if(encoding.toLocaleLowerCase() === 'ascii') {
diff --git a/src/ios/RNFetchBlobFS.m b/src/ios/RNFetchBlobFS.m
index b97a73e83..cb7aae891 100644
--- a/src/ios/RNFetchBlobFS.m
+++ b/src/ios/RNFetchBlobFS.m
@@ -213,49 +213,32 @@ + (void) writeFile:(NSString *)path encoding:(NSString *)encoding data:(NSString
         encoding = [encoding lowercaseString];
         if(![fm fileExistsAtPath:folder]) {
             [fm createDirectoryAtPath:folder withIntermediateDirectories:YES attributes:NULL error:&err];
+            [fm createFileAtPath:path contents:nil attributes:nil];
         }
-        // if file exists, write file using encoding
-        if(![fm fileExistsAtPath:path]) {
-            if([encoding isEqualToString:@"base64"]){
-                NSData * byteData = [[NSData alloc] initWithBase64EncodedString:data options:0];
-                [fm createFileAtPath:path contents:byteData attributes:NULL];
-            }
-            // write file from file
-            else if([encoding isEqualToString:@"uri"]) {
-                [[self class] writeFileFromFile:data toFile:path append:append];
-                resolve([NSNull null]);
-                return;
-            }
-            //TODO: from buffer
-            // else if ([encoding isEqualToString:@"buffer"]){
-            // }
-            // write data as UTF8 string
-            else
-                [fm createFileAtPath:path contents:[data dataUsingEncoding:NSUTF8StringEncoding] attributes:NULL];
+        if(err != nil) {
+            reject(@"RNFetchBlob writeFile Error", @"could not create file at path", path);
+            return;
+        }
+        NSFileHandle *fileHandle = [NSFileHandle fileHandleForWritingAtPath:path];
+        NSData * content = nil;
+        if([encoding isEqualToString:@"base64"]) {
+            content = [[NSData alloc] initWithBase64EncodedString:data options:0];
+        }
+        else if([encoding isEqualToString:@"uri"]) {
+            [[self class] writeFileFromFile:data toFile:path append:append];
+            resolve([NSNull null]);
+            return;
         }
-        // file does not exists, create one
         else {
-            NSFileHandle *fileHandle = [NSFileHandle fileHandleForWritingAtPath:path];
-            NSData * content = nil;
-            if([encoding isEqualToString:@"base64"]) {
-                content = [[NSData alloc] initWithBase64EncodedString:data options:0];
-            }
-            else if([encoding isEqualToString:@"uri"]) {
-                [[self class] writeFileFromFile:data toFile:path append:append];
-                resolve([NSNull null]);
-                return;
-            }
-            else {
-                content = [data dataUsingEncoding:NSUTF8StringEncoding];
-            }
-            if(append == YES) {
-                [fileHandle seekToEndOfFile];
-                [fileHandle writeData:content];
-                [fileHandle closeFile];
-            }
-            else {
-                [content writeToFile:path atomically:YES];
-            }
+            content = [data dataUsingEncoding:NSUTF8StringEncoding];
+        }
+        if(append == YES) {
+            [fileHandle seekToEndOfFile];
+            [fileHandle writeData:content];
+            [fileHandle closeFile];
+        }
+        else {
+            [content writeToFile:path atomically:YES];
         }
         fm = nil;
         resolve([NSNull null]);
diff --git a/src/ios/RNFetchBlobNetwork.m b/src/ios/RNFetchBlobNetwork.m
index bcf327861..e33b729b0 100644
--- a/src/ios/RNFetchBlobNetwork.m
+++ b/src/ios/RNFetchBlobNetwork.m
@@ -134,8 +134,6 @@ - (void) sendRequest:(NSDictionary  * _Nullable )options
 
         if(path != nil)
             destPath = path;
-        // else
-        //     destPath = [RNFetchBlobFS getTempPath:cacheKey withExtension:[self.options valueForKey:CONFIG_FILE_EXT]];
     }
     else
     {
diff --git a/src/ios/RNFetchBlobReqBuilder.m b/src/ios/RNFetchBlobReqBuilder.m
index 794826e88..4ab83915a 100644
--- a/src/ios/RNFetchBlobReqBuilder.m
+++ b/src/ios/RNFetchBlobReqBuilder.m
@@ -86,7 +86,13 @@ +(void) buildOctetRequest:(NSDictionary *)options
         if([[method lowercaseString] isEqualToString:@"post"] || [[method lowercaseString] isEqualToString:@"put"]) {
             // generate octet-stream body
             if(body != nil) {
-
+                
+                // when headers does not contain a key named "content-type" (case ignored), use default content type
+                if([[self class] getHeaderIgnoreCases:@"content-type" fromHeaders:mheaders] == nil)
+                {
+                    [mheaders setValue:@"application/octet-stream" forKey:@"Content-Type"];
+                }
+                
                 // when body is a string contains file path prefix, try load file from the path
                 if([body hasPrefix:FILE_PREFIX]) {
                     NSString * orgPath = [body substringFromIndex:[FILE_PREFIX length]];
@@ -95,10 +101,6 @@ +(void) buildOctetRequest:(NSDictionary *)options
                     {
                         [RNFetchBlobFS readFile:orgPath encoding:@"utf8" resolver:nil rejecter:nil onComplete:^(NSData *content) {
                             [request setHTTPBody:content];
-                            if([mheaders valueForKey:@"content-type"] == nil)
-                            {
-                                [mheaders setValue:@"application/octet-stream" forKey:@"content-type"];
-                            }
                             [request setHTTPMethod: method];
                             [request setAllHTTPHeaderFields:mheaders];
                             onComplete(request, [content length]);
@@ -110,24 +112,22 @@ +(void) buildOctetRequest:(NSDictionary *)options
                 }
                 // otherwise convert it as BASE64 data string
                 else {
-                    // the body is BASE64 encoded string
-                    if(([mheaders valueForKey:@"content-type"] == nil && [mheaders valueForKey:@"Content-Type"] == nil) ||
-                       ([[[mheaders valueForKey:@"content-type"] lowercaseString] isEqualToString:@"application/octet-stream"] ||
-                        [[[mheaders valueForKey:@"Content-Type"] lowercaseString] isEqualToString:@"application/octet-stream"]))
+                    
+                    NSString * cType = [[self class]getHeaderIgnoreCases:@"content-type" fromHeaders:mheaders];
+                    // when content-type is application/octet* decode body string using BASE64 decoder
+                    if([[cType lowercaseString] hasPrefix:@"application/octet"])
                     {
                         blobData = [[NSData alloc] initWithBase64EncodedString:body options:0];
-                        [mheaders setValue:@"application/octet-stream" forKey:@"Content-Type"];
                         [request setHTTPBody:blobData];
                         size = [blobData length];
                     }
-                    // use the body string as is
+                    // otherwise use the body as-is
                     else
                     {
                         size = [body length];
                         [request setHTTPBody: [body dataUsingEncoding:NSUTF8StringEncoding]];
                     }
                 }
-                
             }
         }
 
@@ -138,21 +138,6 @@ +(void) buildOctetRequest:(NSDictionary *)options
     });
 }
 
-//+(void) buildEncodedRequest:(NSDictionary *)options
-//                   taskId:(NSString *)taskId
-//                   method:(NSString *)method
-//                      url:(NSString *)url
-//                  headers:(NSDictionary *)headers
-//                     body:(NSString *)body
-//               onComplete:(void(^)(NSURLRequest * req, long bodyLength))onComplete
-//{
-//	NSMutableData * formData = [[NSMutableData alloc] init];
-//    
-//	[formData appendData:[[NSString stringWithFormat:@"%@", body] dataUsingEncoding:NSUTF8StringEncoding]];
-//	onComplete(formData);
-//}
-
-
 +(void) buildFormBody:(NSArray *)form boundary:(NSString *)boundary onComplete:(void(^)(NSData * formData))onComplete
 {
     NSMutableData * formData = [[NSMutableData alloc] init];
@@ -225,5 +210,16 @@ void __block (^getFieldData)(id field) = ^(id field)
     }
 }
 
++(NSString *) getHeaderIgnoreCases:(NSString *)field fromHeaders:(NSMutableArray *) headers {
+    
+    NSString * normalCase = [headers valueForKey:field];
+    NSString * ignoredCase = [headers valueForKey:[field lowercaseString]];
+    if( normalCase != nil)
+        return normalCase;
+    else
+        return ignoredCase;
+    
+}
+
 
 @end
diff --git a/src/polyfill/Blob.js b/src/polyfill/Blob.js
index a52d2b38e..a17044c1d 100644
--- a/src/polyfill/Blob.js
+++ b/src/polyfill/Blob.js
@@ -25,7 +25,7 @@ export default class Blob {
 
   _ref:string = null;
   _blobCreated:boolean = false;
-  _onCreated:() => void;
+  _onCreated:Array<any> = [];
 
   static Instances:any = {}
 
@@ -35,86 +35,44 @@ export default class Blob {
     this.cacheName = getBlobName()
     this.isRNFetchBlobPolyfill = true
     this.type = mime
-    log.verbose('Blob constructor called' , data, 'mime', mime)
-
-    if(typeof data === 'string') {
-      // content from file
-      if(data.startsWith('RNFetchBlob-file://')) {
-        this._ref = data
-        this._blobCreated = true
-        if(typeof this._onCreated === 'function')
-          this._onCreated(this)
-      }
-      // content from variable need create file
-      else {
-        log.verbose('create Blob cache file ..')
-        this._ref = RNFetchBlob.wrap(blobCacheDir + this.cacheName)
-        let encoding = 'utf8'
-        if(typeof data === 'string' && String(mime).match('application/octet') )
-          encoding = 'base64'
-        else if(Array.isArray(data))
-          encoding = 'ascii'
-
-        this.init(data, encoding)
-            .then(() => {
-              log.verbose('init executed ')
-              if(typeof this._onCreated === 'function')
-                this._onCreated(this)
-            })
-            .catch((err) => {
-              log.error('RNFetchBlob cannot create Blob', err)
-            })
-      }
+    log.verbose('Blob constructor called', 'mime', mime)
+    this._ref = blobCacheDir + this.cacheName
+    let p = null
+    // content from file
+    if(typeof data === 'string' && data.startsWith('RNFetchBlob-file://')) {
+      log.verbose('create Blob cache file from file path')
+      this._ref = data
+      p = Promise.resolve()
     }
-    // TODO : handle mixed blob array
+    // content from variable need create file
+    else if(typeof data === 'string') {
+      log.verbose('create Blob cache file from string')
+      let encoding = 'utf8'
+      if(String(mime).match('application/octet'))
+        encoding = 'base64'
+      else if(Array.isArray(data))
+        encoding = 'ascii'
+      // create cache file
+      p = fs.writeFile(this._ref, data, encoding)
+
+    }
+    // when input is an array of mixed data types, create a file cache
     else if(Array.isArray(data)) {
-      this._ref = RNFetchBlob.wrap(blobCacheDir + this.cacheName)
-      createMixedBlobData(this._ref, data)
-        .then(() => {
-          if(typeof this._onCreated === 'function')
-            this._onCreated(this)
-        })
+      log.verbose('create Blob cache file from mixed array', data)
+      p = createMixedBlobData(this._ref, data)
     }
+    p && p.then(() => {
+      this._invokeOnCreateEvent()
+    })
+    .catch((err) => {
+      log.error('RNFetchBlob cannot create Blob : '+ this._ref)
+    })
 
   }
 
   onCreated(fn:() => void) {
-    log.verbose('register blob onCreated')
-    if(this._blobCreated)
-      fn()
-    else
-      this._onCreated = fn
-  }
-
-  /**
-   * Create blob file cache
-   * @nonstandard
-   * @param  {string | Array} data Data to create Blob file
-   * @param  {'base64' | 'utf8' | 'ascii'} encoding RNFetchBlob fs encoding
-   * @return {Promise}
-   */
-  init(data, encoding):Promise {
-    return new Promise((resolve, reject) => {
-      fs.exists(blobCacheDir)
-        .then((exist) => {
-          log.verbose('blob cache folder exist', blobCacheDir, exist)
-          let path = String(this._ref).replace('RNFetchBlob-file://', '')
-          log.verbose('create cache file', path)
-          if(!exist)
-            return fs.mkdir(blobCacheDir)
-                     .then(() => fs.createFile(path, data, encoding))
-          else
-            return fs.createFile(path, data, encoding)
-        })
-        .then(() => {
-          this._blobCreated = true
-          resolve()
-        })
-        .catch((err) => {
-          reject(err)
-        })
-    })
-
+    log.verbose('register blob onCreated', this._onCreated.length)
+    this._onCreated.push(fn)
   }
 
   /**
@@ -146,6 +104,21 @@ export default class Blob {
     return fs.unlink(this._ref)
   }
 
+  clearCache() {
+
+  }
+
+  _invokeOnCreateEvent() {
+    log.verbose('invoke create event')
+    this._blobCreated = true
+    let fns = this._onCreated
+    for(let i in fns) {
+      if(typeof fns[i] === 'function')
+        fns[i](this)
+    }
+    delete this._onCreated
+  }
+
 }
 
 /**
@@ -164,15 +137,21 @@ function getBlobName() {
  * @return {Promise}
  */
 function createMixedBlobData(ref, dataArray) {
-  let p = fs.createFile(ref, '')
+  let p = fs.writeFile(ref, '')
+  let args = []
   for(let i in dataArray) {
     let part = dataArray[i]
     if(part instanceof Blob)
-      p.then(() => fs.appendFile(ref, part.getRNFetchBlobRef()), 'uri')
+      args.push([ref, part.getRNFetchBlobRef(), 'uri'])
+    else if(typeof part === 'string')
+      args.push([ref, part, 'utf8'])
     else if (Array.isArray(part))
-      p.then(() => fs.appendFile(ref), part, 'ascii')
-    else
-      p.then(() => fs.appendFile(ref), part, 'utf8')
+      args.push([ref, part, 'ascii'])
   }
-  return p
+  return p.then(() => {
+    let promises = args.map((p) => {
+      return fs.appendFile.call(this, ...p)
+    })
+    return Promise.all(promises)
+  })
 }
diff --git a/src/polyfill/XMLHttpRequest.js b/src/polyfill/XMLHttpRequest.js
index 9f7c2a75e..cf01fe32b 100644
--- a/src/polyfill/XMLHttpRequest.js
+++ b/src/polyfill/XMLHttpRequest.js
@@ -92,8 +92,9 @@ export default class XMLHttpRequest extends XMLHttpRequestEventTarget{
 
     this._upload = new XMLHttpRequestEventTarget()
     log.verbose(typeof body, body instanceof FormData)
-    if(Array.isArray(body)) {
-      // TODO
+
+    if(body instanceof Blob) {
+      body = RNFetchBlob.wrap(body.getRNFetchBlobRef())
     }
 
     this.dispatchEvent('loadstart')
@@ -211,7 +212,7 @@ export default class XMLHttpRequest extends XMLHttpRequestEventTarget{
   }
 
   _onDone(resp) {
-    log.verbose('XMLHttpRequest done', resp.text())
+    log.verbose('XMLHttpRequest done', this)
     this.statusText = '200 OK'
     this._status = 200
     switch(resp.type) {