doc (readme): added link to tuotrial

README.md

@@ -84,6 +84,11 @@ Please follow this guidelines when reporting bugs and feature requests:
 
 Thanks for understanding!
 
+# Tutorial with backend implmentation 
+
+- [Complete example with backend implementation in Node.js](https://ciphertrick.com/file-upload-angular-nodejs/). 
+
+
 ### License
 
 The MIT License (see the [LICENSE](https://github.com/valor-software/ng2-file-upload/blob/master/LICENSE) file for the full text)

src/file-upload/file-uploader.class.ts

@@ -39,12 +39,12 @@ export interface FileUploaderOptions {
   parametersBeforeFiles?: boolean;
   formatDataFunction?: Function;
   formatDataFunctionIsAsync?: boolean;
-  parallelUploads?: number;
 }
 
 export class FileUploader {
 
   public authToken: string;
+  public isUploading: boolean = false;
   public queue: FileItem[] = [];
   public progress: number = 0;
   public _nextIndex: number = 0;
@@ -52,10 +52,6 @@ export class FileUploader {
   public authTokenHeader: string;
   public response: EventEmitter<any>;
 
-  public get isUploading(): boolean {
-    return this.queue.some((item: FileItem) => item.isUploading);
-  }
-
   public options: FileUploaderOptions = {
     autoUpload: false,
     isHTML5: true,
@@ -93,8 +89,8 @@ export class FileUploader {
       this.options.filters.unshift({ name: 'mimeType', fn: this._mimeTypeFilter });
     }
 
-    for (let item of this.queue) {
-      item.url = this.options.url;
+    for (let i = 0; i < this.queue.length; i++) {
+      this.queue[ i ].url = this.options.url;
     }
   }
 
@@ -154,6 +150,10 @@ export class FileUploader {
     let item = this.queue[ index ];
     let transport = this.options.isHTML5 ? '_xhrTransport' : '_iframeTransport';
     item._prepareToUploading();
+    if (this.isUploading) {
+      return;
+    }
+    this.isUploading = true;
     (this as any)[ transport ](item);
   }
 
@@ -172,10 +172,7 @@ export class FileUploader {
       return;
     }
     items.map((item: FileItem) => item._prepareToUploading());
-    let numberUploadsToStart = Math.min(items.length, this.options.parallelUploads || 1);
-    for (let i = 0; i < numberUploadsToStart; ++i) {
-      items[ i ].upload();
-    }
+    items[ 0 ].upload();
   }
 
   public cancelAll(): void {
@@ -279,6 +276,7 @@ export class FileUploader {
     item._onComplete(response, status, headers);
     this.onCompleteItem(item, response, status, headers);
     let nextItem = this.getReadyItems()[ 0 ];
+    this.isUploading = false;
     if (nextItem) {
       nextItem.upload();
       return;
@@ -375,7 +373,7 @@ export class FileUploader {
     }
     xhr.onreadystatechange = function () {
       if (xhr.readyState == XMLHttpRequest.DONE) {
-        that.response.emit(xhr.responseText);
+        that.response.emit(xhr.responseText)
       }
     }
     if (this.options.formatDataFunctionIsAsync) {