Usage

By default, Raven makes a few efforts to try its best to capture meaningful stack traces, but browsers make it pretty difficult.

The easiest solution is to prevent an error from bubbling all of the way up the stack to window.

Reporting Errors Correctly

There are different methods to report errors and this all depends a little bit on circumstances.

try … catch

The simplest way, is to try and explicitly capture and report potentially problematic code with a try...catch block and Raven.captureException.

try {
    doSomething(a[0])
} catch(e) {
    Raven.captureException(e)
}

Do not throw strings! Always throw an actual Error object. For example:

throw new Error('broken')  // good
throw 'broken'  // bad

It’s impossible to retrieve a stack trace from a string. If this happens, Raven transmits the error as a plain message.

context/wrap

Raven.context allows you to wrap any function to be immediately executed. Behind the scenes, Raven is just wrapping your code in a try...catch block to record the exception before re-throwing it.

Raven.context(function() {
    doSomething(a[0])
})

Raven.wrap wraps a function in a similar way to Raven.context, but instead of executing the function, it returns another function. This is especially useful when passing around a callback.

var doIt = function() {
    // doing cool stuff
}

setTimeout(Raven.wrap(doIt), 1000)

Tracking Users

While a user is logged in, you can tell Sentry to associate errors with user data.

Raven.setUserContext({
    email: 'matt@example.com',
    id: '123'
})

If at any point, the user becomes unauthenticated, you can call Raven.setUserContext() with no arguments to remove their data. This would only really be useful in a large web app where the user logs in/out without a page reload.

This data is generally submitted with each error or message and allows you to figure out which users are affected by problems.

Capturing Messages

Raven.captureMessage('Broken!')

Passing Additional Data

The captureMessage, captureException, context, and wrap functions all allow passing additional data to be tagged onto the error.

level

The log level associated with this event. Default: error

Raven.captureMessage('Something happened', {
  level: 'info' // one of 'info', 'warning', or 'error'
});
logger

The name of the logger used to record this event. Default: javascript

Raven.captureException(new Error('Oops!'), {
  logger: 'my.module'
});

Note that logger can also be set globally via Raven.config.

tags

Tags to assign to the event.

Raven.wrap({
  tags: {git_commit: 'c0deb10c4'}
}, function () { /* ... */ });

// NOTE: Raven.wrap and Raven.context accept options as first argument

You can also set tags globally to be merged in with future exceptions events via Raven.config, or Raven.setTagsContext:

Raven.setTagsContext({ key: "value" });
extra

Arbitrary data to associate with the event.

Raven.context({
  extra: {planet: {name: 'Earth'}}
}, function () { /* ... */ });

// NOTE: Raven.wrap and Raven.context accept options as first argument

You can also set extra data globally to be merged in with future events with setExtraContext:

Raven.setExtraContext({ foo: "bar" })

Recording Breadcrumbs

Breadcrumbs are browser and application lifecycle events that are helpful in understanding the state of the application leading up to a crash.

By default, Raven.js instruments browser built-ins and DOM events to automatically collect a few useful breadcrumbs for you:

  • XMLHttpRequests
  • URL / address bar changes
  • UI clicks and keypress DOM events
  • console log statements
  • previous errors

You can also record your own breadcrumbs:

Raven.captureBreadcrumb({
  message: 'Item added to shopping cart',
  category: 'action',
  data: {
     isbn: '978-1617290541',
     cartSize: '3'
  }
});

To learn more about what types of data can be collected via breadcrumbs, see the breadcrumbs client API specification.

Note that you can also disable automatic breadcrumb collection entirely or disable specific collectors:

Raven.config('___PUBLIC_DSN___', {
  autoBreadcrumbs: {
    xhr: false
  }
});

For more on configuring breadcrumbs, see Configuration.

Getting Back an Event ID

An event id is a globally unique id for the event that was just sent. This event id can be used to find the exact event from within Sentry.

This is often used to display for the user and report an error to customer service.

Raven.lastEventId()

Raven.lastEventId() will be undefined until an event is sent. After an event is sent, it will contain the string id.

Raven.captureMessage('Broken!')
alert(Raven.lastEventId())

User Feedback

Often you might find yourself wanting to collect additional feedback from the user. Sentry supports this via an embeddable widget.

try {
    handleRouteChange(...)
} catch (err) {
    Raven.captureException(err);
    Raven.showReportDialog();
}

For more details on this feature, see the User Feedback guide.

Verify Raven Setup

If you need to conditionally check if raven needs to be initialized or not, you can use the isSetup function. It will return true if Raven is already initialized:

Raven.isSetup()

Dealing with Minified Source Code

Raven and Sentry support Source Maps.

We have provided some instructions to creating Source Maps over at https://docs.sentry.io/hosted/clients/javascript/sourcemaps/. Also, checkout our Gruntfile for a good example of what we’re doing.

You can use Source Map Validator to help verify that things are correct.

CORS

If you’re hosting your scripts on another domain and things don’t get caught by Raven, it’s likely that the error will bubble up to window.onerror. If this happens, the error will report some ugly Script error and Raven will drop it on the floor since this is a useless error for everybody.

To help mitigate this, we can tell the browser that these scripts are safe and we’re allowing them to expose their errors to us.

In your <script> tag, specify the crossorigin attribute:

<script src="//cdn.example.com/script.js" crossorigin="anonymous"></script>

And set an Access-Control-Allow-Origin HTTP header on that file.

Access-Control-Allow-Origin: *

Note

both of these steps need to be done or your scripts might not even get executed

Promises

By default, Raven.js does not capture unhandled promise rejections.

Most Promise libraries have a global hook for capturing unhandled errors. You will need to manually hook into such an event handler and call Raven.captureException or Raven.captureMessage directly.

For example, the RSVP.js library (used by Ember.js) allows you to bind an event handler to a global error event:

RSVP.on('error', function(reason) {
    Raven.captureException(reason);
});

Bluebird and other promise libraries report unhandled rejections to a global DOM event, unhandledrejection:

window.onunhandledrejection = function(evt) {
    Raven.captureException(evt.reason);
};

Please consult your promise library documentation on how to hook into its global unhandled rejection handler, if it exposes one.

Custom Grouping Behavior

In some cases you may see issues where Sentry groups multiple events together when they should be separate entities. In other cases, Sentry simply doesn’t group events together because they’re so sporadic that they never look the same.

Both of these problems can be addressed by specifying the fingerprint attribute.

For example, if you have HTTP 404 (page not found) errors, and you’d prefer they deduplicate by taking into account the URL:

Raven.captureException(ex, {fingerprint: ['{{ default }}', 'http://my-url/']});

For more information, see Customize Grouping with Fingerprints.

Preventing Abuse

By default, the Sentry server accepts errors from any host. This can lead to an abuse scenario where a malicious party triggers JavaScript errors from a different website that are accepted by your Sentry Project. To prevent this, it is recommended to whitelist known hosts where your JavaScript code is operating.

This setting can be found under the Project Settings page in Sentry. You’ll need to add each domain that you plan to report from into the Allowed Domains box. When an error is collected by Raven.js and transmitted to Sentry, Sentry will verify the Origin and/or Referer headers of the HTTP request to verify that it matches one of your allowed hosts.