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Ilya Kantor 2017-01-29 02:57:35 +03:00
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1-js/08-error-handling/1-try-catch/article.md
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@ -575,11 +575,11 @@ In the code above, an error inside `try` always falls out, because there's no `c
The information from this section is not a part of the core Javascript.
```
Let's imagine we've got a fatal error outside of `try..catch`, and the script died. Like a programming error that no `try..catch` doesn't know how to handle, or something else terrible.
Let's imagine we've got a fatal error outside of `try..catch`, and the script died. Like a programming error or something else terrible.
Is there a way to react on such happening? We may want to log the error, show something to the user (normally he doesn't see the error message) etc.
Is there a way to react on such a happening? We may want to log the error, show something to the user (normally he doesn't see error messages) etc.
There is none in the specification, but environments usually provide it, because it's really handy. For instance, Node.JS has [process.on('uncaughtException')](https://nodejs.org/api/process.html#process_event_uncaughtexception) for that. And in the browser we can assign a function to special [window.onerror](mdn:api/GlobalEventHandlers/onerror) property. It will run in case of an uncaught error.
There is none in the specification, but environments usually provide it, because it's really useful. For instance, Node.JS has [process.on('uncaughtException')](https://nodejs.org/api/process.html#process_event_uncaughtexception) for that. And in the browser we can assign a function to special [window.onerror](mdn:api/GlobalEventHandlers/onerror) property. It will run in case of an uncaught error.
The syntax:
@ -621,7 +621,14 @@ For instance:
The role of the global handler `window.onerror` is usually not to recover the script execution -- that's probably impossible in case of programming errors, but to send the error message to developers.
There are also web-services that provide error-logging facilities for such cases, like <https://errorception.com> or <http://www.muscula.com>. They give a script with custom `window.onerror` function, and once inserted into a page, it reports about all errors it gets to their server. Afterwards developers can browse them and get notifications on email about fresh errors.
There are also web-services that provide error-logging for such cases, like <https://errorception.com> or <http://www.muscula.com>.
They work like this:
1. We register at the service and get a piece of JS (or a script URL) from them to insert on pages.
2. That JS script has a custom `window.onerror` function.
3. When an error occurs, it sends a network request about it to the service.
4. We can log in to the service web interface and see errors.
## Summary