How to handle file download error in js

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All the code samples and API provided by the authors are solely their creation and neither the author nor the site are responsible if it does not work as intended. How do you keep the file type though? Creating a blob, you would lose that file type entirely. Let's say it's an mp4 video file, how do you detect that and rebuild it as the right file type? Jim "How do you keep the file type though?

Though note, user could change suggested file name or extension at Save File dialog — guest Jim See version 3 at plnkr. Community Bot 1 1 1 silver badge. Tomasz Dziuda Tomasz Dziuda 1 1 silver badge 4 4 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown.

I will skip the part that gets tight-coupled to the DOM. There is no difference here from the bad handler you saw. A definite improvement over the bad handler. Here the exception gets bubbled through the call stack.

What I like is now errors will unwind the stack which is super helpful in debugging. With an exception, the interpreter travels up the stack looking for another handler. This opens many opportunities to deal with errors at the top of the call stack.

Unfortunately, since it is an ugly handler I lose the original error. So I am forced to traverse back down the stack to figure out the original exception. With this at least I know something went wrong, which is why you throw an exception. As an alternative, is is possible to end the ugly handler with a custom error.

When you add more details to an error it is no longer ugly but helpful. The key is to append specific information about the error. The specified error adds more details and keeps the original error message. With this improvement it is no longer an ugly handler but clean and useful. With these handlers, I still get an unhandled exception.

So, one way to unwind exceptions is to place a try But, remember I said the browser is event-driven? Yes, an exception in JavaScript is no more than an event. The interpreter halts execution in the executing context and unwinds. Turns out, there is an onerror global event handler we can use. This event handler catches errors within any executing context. Error events get fired from various targets for any kind of error. What is so radical is this event handler centralizes error handling in the code.

Like with any other event, you can daisy chain handlers to handle specific errors. These handlers can get registered at any time. The interpreter will cycle through as many handlers as it needs to. The code base gets freed from try The key is to treat error handling like event handling in JavaScript. The call stack is super helpful in troubleshooting issues.

The good news is that the browser provides this information out of the box. Usually in client-side code value can be any JavaScript value including a string, a number or an object.

An error object is an object that is either an instance of the Error object, or extends the Error class, provided in the Error core module :. Any exception raised in the lines of code included in the try block is handled in the corresponding catch block:.