CODEWITHSUNDEEP
javascriptbrowserdownload
user2866134
user2866134

Reputation: 41

How Browser detects that file has been downloaded completely

I want to know that how browsers detect that file has been downloaded.I also want to know that can we take control over File Download dialogue through java-script. I have done enough Googling but I didn't get success.Please help me. Thanks in Advance

Upvotes: 0

Views: 392

Answers (1)

Niet the Dark Absol
Niet the Dark Absol

Reputation: 324630

When downloading a file, the server includes a Content-Length header indicating how many bytes long the response is. The browser uses this to give you a percentage of completion. You may notice in some cases that this header is missing (generally true of streams, but also exporting files in PHPMyAdmin) and in this case the browser will just tell you how much data has been downloaded so far.

You can use AJAX to download a file, and generally this is used for cache purposes (I use it in my HTML5 games to preload JavaScript files that will be needed later) and in some browsers you can check if the readyState is 3, then check the length of the responseText so far against the Content-Length header to get a percentage - but be warned that some browsers don't like that and will throw an error if you try to access responseText before readyState is 4.

Upvotes: 2

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