Browse files

Article - Really simple file uploads

  • Loading branch information...
1 parent f1ddf5a commit 78e21b7d5503a5b2b372f6c2a5de077a1e809267 @Srirangan Srirangan committed Feb 5, 2012
Showing with 86 additions and 0 deletions.
  1. +86 −0 articles/really-simple-file-uploads.markdown
@@ -0,0 +1,86 @@
+Title: Really simple file uploads with Express
+Author: Srirangan
+Date: Sun Feb 05 2012 11:00:00 GMT+0530 (IST)
+Node: v0.6.10
+Few days ago I was working on a fairly typical web application and I faced the challenge of implementing a fairly
+typical web application feature - file uploads. It was the first time I was implementing file uploads with Node (and
+Express) and I did what anyone else would do - I googled it.
+Unfortunately all the articles / posts out there are either outdated, too complex or plain wrong. So I did the next
+most obvious thing - post a question on the mailing list. As always Mr. Holowaychuk was incredibly quick to respond.
+His answer lead me to do what I should have done in the first place - read the docs.
+### The upload form
+This is the most obvious part of the challenge. You're probably familiar with this already. Anyway, for the sake of
+completeness of this article, here it is.
+You will need a form in your browser for the file upload. I use Jade to generate my HTML and here how it looks:
+ form(action="...", method="post", enctype="multipart/form-data")
+ input(type="file", name="displayImage")
+The *form.action* will point to a route that handles the file upload. More below.
+### Accessing the uploaded file
+If you're using recents versions of Node and Express, file uploads are a piece of cake. And I'll back this claim but
+before we go any further make sure you're familiar with [routes, requests and responses in Express](
+Okay, now let's justify the "piece of cake" claim. In our file upload route, the *req* parameter has *req.files*
+available. Here's an example of what the *req.files* would contain:
+ {
+ displayImage: {
+ size: 11885,
+ path: '/tmp/1574bb60b4f7e0211fd9ab48f932f3ab',
+ name: 'avatar.png',
+ type: 'image/png',
+ lastModifiedDate: Sun, 05 Feb 2012 05:31:09 GMT,
+ _writeStream: {
+ path: '/tmp/1574bb60b4f7e0211fd9ab48f932f3ab',
+ fd: 14,
+ writable: false,
+ flags: 'w',
+ encoding: 'binary',
+ mode: 438,
+ bytesWritten: 11885,
+ busy: false,
+ _queue: [],
+ drainable: true
+ },
+ length: [Getter],
+ filename: [Getter],
+ mime: [Getter]
+ }
+ }
+In the *req.files* object above, the property *displayImage* is the name of the file field in your HTML form and
+*req.files* will contain one property each for every valid HTML file form field.
+The file object contains the *type*, *size* and *name* properties for your server side validations.
+### Saving the uploaded file
+Assuming the file is valid, you use the *path* property for the next step. The *path* would typically contain a location
+in the *tmp* folder. Your application logic could either require you to access the contents of the file or simply move
+the uploaded file to another location.
+ fs.readFile(req.files.displayImage.path, function (err, data) {
+ // ...
+ var newPath = __dirname + "/uploads/uploadedFileName";
+ fs.writeFile(newPath, data, function (err) {
+ res.redirect("back");
+ });
+ });
+In the *fs.readFile* callback, we have the *data* parameter through which we can access the contents of the file. The
+example above is taken from an application that needed to modify the file and save it in a new location. Thus
+*fs.writeFile* is used to write *data* to the *newPath*.
+If your app needs to simply move the uploaded file without modifying the contents *fs.rename* can be used as more
+simpler option.
+That's all there is to it. I've done file uploads in many server side languages including Python, Java, Scala and PHP
+and I don't think its ever been this simple. So much for JavaScript being labeled as an inferior server side language.

0 comments on commit 78e21b7

Please sign in to comment.