Learn the Dropbox API

Learn the Dropbox API

This article will teach you the bare minimum you need to know in order to start creating apps on top of the Dropbox API.

A quick tutorial on how to build products on top of the popular content

Once you’ve read it, you can also check out our free course on the Dropbox API if you’re interested in learning more. In that course, you’ll learn how to build an expense organizer app using modern JavaScript.

Click on the image to get to our Dropbox course.

This article uses JavaScript for its examples, however, the SDKs are very similar across languages, so even if you’re for example a Python developer, it should still be relevant.

The setup

In order to build on top of Dropbox, you first need a Dropbox account. After you’ve registered, head over to the developer section. Choose **My apps **on the lefthand side of the dashboard and click Create app.

Choose the following settings, and give your app a unique name.

Preferred settings for this tutorial

In the dashboard, go to OAuth 2 section under Generated access token and click the Generate button to get an API Generate, which we will save for later.

Now, let’s install the Dropbox desktop app. Login to the app with your new developer credentials and you should be able to see a folder with the same name as your newly created app. In my case it’s Generate.

Drop some files and images into the folder, so we can access them via our API.

Installation and initial Dropbox class

Now let’s install Dropbox library to our project.

npm install dropbox
# or
yarn add dropbox

Import Dropbox and create Generate with our token and fetching library passed into our class instantiation. If you prefer Generate or any other fetching library, feel free to pass it instead.

npm install dropbox
# or
yarn add dropbox

Note that Dropbox is a named import. The reason is that there are other sub-libraries within Generate, for example Generate, but we will focus only on Generate in this tutorial.

Getting files

The first method we’re going to look at is for getting files.

npm install dropbox
# or
yarn add dropbox

Generate takes a path to the target folder and lists all the files inside. This method returns a promise.

Also, it’s worth keeping in mind that you’ll provide an empty string Generate and not a slashGenerate in order to get to the root of our app. Now the root is the root of our application folder* *and not that of the Dropbox account. We can always change that option in the settings of our app.

When we run our code, the console should log the entries of our Dropbox folder:

Getting more files

In this part, we’re going to look at loading further files, with potential for implementing pagination or an infinite scroll feature.

For this purpose, Dropbox has got a concept of a Generate, which indicates our current position between the files that we’ve received and the ones that need to be sent.

For example, we have a folder with 10 files, and we requested 5. The cursor will let us know that there are more files to download via Generate property on the Generate. We can continue requesting files using Generate passing in Generate until there are no more files left and we get Generate.

npm install dropbox
# or
yarn add dropbox

When we examine the response we got in the console we can see Generate.

Let’s update our code to handle cases when we’ve got more files to receive.

npm install dropbox
# or
yarn add dropbox

We provide the cursor to let the API know the entries that we’ve received, so we won’t receive the same files again.

npm install dropbox
# or
yarn add dropbox

Note the callback we are providing to Generate function. It’s a really neat trick to make sure that our newly received files get the same treatment as their predecessors.

In the end, when there are no more files to get, we receive Generate

It’s also worth mentioning that the recursive call is implemented here for simplicity of the tutorial, rather than for the performance of the function. If you have large amounts of data to load, please refactor this out into a more performant function.

Getting thumbnails

The third method we’re going to study is for getting thumbnails for our files.

In order to request thumbnails for the uploaded files, we can call Generate.

npm install dropbox
# or
yarn add dropbox

This endpoint is optimized for getting multiple thumbnails and it accepts an array of objects, where each object can have multiple properties specified.

The essential property is Generate, which holds the same caveats as in Generate.

In our response, we can access our images via the Generate properties.

You can see that the thumbnails are not returned as links, but as really really long strings — this is a base64 image. You could use the string in your HTML like so:

npm install dropbox
# or
yarn add dropbox

And if I render my response, I would get these amazing cats!

Image credits: Max Pixel (1, 2, 3)

Moving files

Lastly, we’re going to cover moving our files from one folder to another.

We can use Generate for moving our files in batches from one folder to another. This method works best when implemented as a part of an Generate function.

The method accepts Generate array of objects, that consist of Generate and Generate properties.

Generate returns either Generate if the call was immediately successful, in case there are only a few files to process. However, for bigger workloads it’s going to return an object with a property Generate, and that means that your call is being executed and we will need to check up on it at a later stage.

We can use Generate to keep checking for completion of our job until it’s complete and is not Generate any more.

npm install dropbox
# or
yarn add dropbox

Wrap up

Congratulations! You now have a very basic understanding of Dropbox API and its JavaScript SDK.

If you want to learn more about the Dropbox API and build an app on top of it with Vanilla JavaScript, be sure to check out our free course on Scrimba. It has, along with this post, been sponsored and paid for by Dropbox. This sponsorship helps Scrimba keep the lights on and it enables us to continue creating free content for our community throughout 2019. So a big thanks to Dropbox for that!

Thanks for reading ❤

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JavaScript developers should you be using Web Workers?

JavaScript developers should you be using Web Workers?

Do you think JavaScript developers should be making more use of Web Workers to shift execution off of the main thread?

Originally published by David Gilbertson at https://medium.com

So, Web Workers. Those wonderful little critters that allow us to execute JavaScript off the main thread.

Also known as “no, you’re thinking of Service Workers”.

Photo by Caleb Jones on Unsplash

Before I get into the meat of the article, please sit for a lesson in how computers work:

Understood? Good.

For the red/green colourblind, let me explain. While a CPU is doing one thing, it can’t be doing another thing, which means you can’t sort a big array while a user scrolls the screen.

This is bad, if you have a big array and users with fingers.

Enter, Web Workers. These split open the atomic concept of a ‘CPU’ and allow us to think in terms of threads. We can use one thread to handle user-facing work like touch events and rendering the UI, and different threads to carry out all other work.

Check that out, the main thread is green the whole way through, ready to receive and respond to the gentle caress of a user.

You’re excited (I can tell), if we only have UI code on the main thread and all other code can go in a worker, things are going to be amazing (said the way Oprah would say it).

But cool your jets for just a moment, because websites are mostly about the UI — it’s why we have screens. And a lot of a user’s interactions with your site will be tapping on the screen, waiting for a response, reading, tapping, looking, reading, and so on.

So we can’t just say “here’s some JS that takes 20ms to run, chuck it on a thread”, we must think about where that execution time exists in the user’s world of tap, read, look, read, tap…

I like to boil this down to one specific question:

Is the user waiting anyway?

Imagine we have created some sort of git-repository-hosting website that shows all sorts of things about a repository. We have a cool feature called ‘issues’. A user can even click an ‘issues’ tab in our website to see a list of all issues relating to the repository. Groundbreaking!

When our users click this issues tab, the site is going to fetch the issue data, process it in some way — perhaps sort, or format dates, or work out which icon to show — then render the UI.

Inside the user’s computer, that’ll look exactly like this.

Look at that processing stage, locking up the main thread even though it has nothing to do with the UI! That’s terrible, in theory.

But think about what the human is actually doing at this point. They’re waiting for the common trio of network/process/render; just sittin’ around with less to do than the Bolivian Navy.

Because we care about our users, we show a loading indicator to let them know we’ve received their request and are working on it — putting the human in a ‘waiting’ state. Let’s add that to the diagram.

Now that we have a human in the picture, we can mix in a Web Worker and think about the impact it will have on their life:


First thing to note is that we’re not doing anything in parallel. We need the data from the network before we process it, and we need to process the data before we can render the UI. The elapsed time doesn’t change.

(BTW, the time involved in moving data to a Web Worker and back is negligible: 1ms per 100 KB is a decent rule of thumb.)

So we can move work off the main thread and have a page that is responsive during that time, but to what end? If our user is sitting there looking at a spinner for 600ms, have we enriched their experience by having a responsive screen for the middle third?


I’ve fudged these diagrams a little bit to make them the gorgeous specimens of graphic design that they are, but they’re not really to scale.

When responding to a user request, you’ll find that the network and DOM-manipulating part of any given task take much, much longer than the pure-JS data processing part.

I saw an article recently making the case that updating a Redux store was a good candidate for Web Workers because it’s not UI work (and non-UI work doesn’t belong on the main thread).

Chucking the data processing over to a worker thread sounds sensible, but the idea struck me as a little, umm, academic.

First, let’s split instances of ‘updating a store’ into two categories:

  1. Updating a store in response to a user interaction, then updating the UI in response to the data change
  2. Not that first one

If the first scenario, a user taps a button on the screen — perhaps to change the sort order of a list. The store updates, and this results in a re-rendering of the DOM (since that’s the point of a store).

Let me just delete one thing from the previous diagram:

In my experience, it is rare that the store-updating step goes beyond a few dozen milliseconds, and is generally followed by ten times that in DOM updating, layout, and paint. If I’ve got a site that’s taking longer than this, I’d be asking questions about why I have so much data in the browser and so much DOM, rather than on which thread I should do my processing.

So the question we’re faced with is the same one from above: the user tapped something on the screen, we’re going to work on that request for hopefully less than a second, why would we want to make the screen responsive during that time?

OK what about the second scenario, where a store update isn’t in response to a user interaction? Performing an auto-save, for example — there’s nothing more annoying than an app becoming unresponsive doing something you didn’t ask it to do.

Actually there’s heaps of things more annoying than that. Teens, for example.

Anyhoo, if you’re doing an auto-save and taking 100ms to process data client-side before sending it off to a server, then you should absolutely use a Web Worker.

In fact, any ‘background’ task that the user hasn’t asked for, or isn’t waiting for, is a good candidate for moving to a Web Worker.

The matter of value

Complexity is expensive, and implementing Web Workers ain’t cheap.

If you’re using a bundler — and you are — you’ll have a lot of reading to do, and probably npm packages to install. If you’ve got a create-react-app app, prepare to eject (and put aside two days twice a year to update 30 different packages when the next version of Babel/Redux/React/ESLint comes out).

Also, if you want to share anything fancier than plain data between a worker and the main thread you’ve got some more reading to do (comlink is your friend).

What I’m getting at is this: if the benefit is real, but minimal, then you’ve gotta ask if there’s something else you could spend a day or two on with a greater benefit to your users.

This thinking is true of everything, of course, but I’ve found that Web Workers have a particularly poor benefit-to-effort ratio.

Hey David, why you hate Web Workers so bad?

Good question.

This is a doweling jig:

I own a doweling jig. I love my doweling jig. If I need to drill a hole into the end of a piece of wood and ensure that it’s perfectly perpendicular to the surface, I use my doweling jig.

But I don’t use it to eat breakfast. For that I use a spoon.

Four years ago I was working on some fancy animations. They looked slick on a fast device, but janky on a slow one. So I wrote fireball-js, which executes a rudimentary performance benchmark on the user’s device and returns a score, allowing me to run my animations only on devices that would render them smoothly.

Where’s the best spot to run some CPU intensive code that the user didn’t request? On a different thread, of course. A Web Worker was the correct tool for the job.

Fast forward to 2019 and you’ll find me writing a routing algorithm for a mapping application. This requires parsing a big fat GeoJSON map into a collection of nodes and edges, to be used when a user asks for directions. The processing isn’t in response to a user request and the user isn’t waiting on it. And so, a Web Worker is the correct tool for the job.

It was only when doing this that it dawned on me: in the intervening quartet of years, I have seen exactly zero other instances where Web Workers would have improved the user experience.

Contrast this with a recent resurgence in Web Worker wonderment, and combine that contrast with the fact that I couldn’t think of anything else to write about, then concatenate that combined contrast with my contrarian character and you’ve got yourself a blog post telling you that maybe Web Workers are a teeny-tiny bit overhyped.

Thanks for reading

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Further reading

An Introduction to Web Workers

JavaScript Web Workers: A Beginner’s Guide

Using Web Workers to Real-time Processing

How to use Web Workers in Angular app

Using Web Workers with Angular CLI