--- title: "Tips and Tricks" url: https://docs.sentry.io/platforms/javascript/legacy-sdk/tips/ --- # Tips and Tricks | Sentry for JavaScript These are some general recommendations and tips for how to get the most out of Raven.js and Sentry. ## [Decluttering Sentry](https://docs.sentry.io/platforms/javascript/legacy-sdk/tips.md#decluttering-sentry) The first thing to do is to consider limiting exceptions to those raised from a list of allowed domains. If your scripts are loaded from `cdn.example.com` and your site is `example.com` it’d be reasonable to set `whitelistUrls` to: ```javascript whitelistUrls: [/https?:\/\/((cdn|www)\.)?example\.com/]; ``` Since this accepts a regular expression, that would catch anything \*.example.com or example.com exactly. See also: [Config: whitelistUrls](https://docs.sentry.io/platforms/javascript/legacy-sdk/config.md#config-whitelist-urls). Next, check out the list of [*integrations*](https://docs.sentry.io/platforms/javascript/legacy-sdk/integrations.md) we provide and see which are applicable to you. The community has compiled a list of common ignore rules for common things, like Facebook, Chrome extensions, etc. So it’s recommended to at least check these out and see if they apply to you. [Check out the original gist](https://gist.github.com/Chocksy/e9b2cdd4afc2aadc7989762c4b8b495a). ```javascript const sentryOptions = { ignoreErrors: [ // Random plugins/extensions "top.GLOBALS", // See: http://blog.errorception.com/2012/03/tale-of-unfindable-js-error.html "originalCreateNotification", "canvas.contentDocument", "MyApp_RemoveAllHighlights", "http://tt.epicplay.com", "Can't find variable: ZiteReader", "jigsaw is not defined", "ComboSearch is not defined", "http://loading.retry.widdit.com/", "atomicFindClose", // Facebook borked "fb_xd_fragment", // ISP "optimizing" proxy - `Cache-Control: no-transform` seems to reduce this. (thanks @acdha) // See http://stackoverflow.com/questions/4113268/how-to-stop-javascript-injection-from-vodafone-proxy "bmi_SafeAddOnload", "EBCallBackMessageReceived", // See http://toolbar.conduit.com/Developer/HtmlAndGadget/Methods/JSInjection.aspx "conduitPage", // Generic error code from errors outside the security sandbox // You can delete this if using raven.js > 1.0, which ignores these automatically. "Script error.", // Avast extension error "_avast_submit", ], denyUrls: [ // Google Adsense /pagead\/js/i, // Facebook flakiness /graph\.facebook\.com/i, // Facebook blocked /connect\.facebook\.net\/en_US\/all\.js/i, // Woopra flakiness /eatdifferent\.com\.woopra-ns\.com/i, /static\.woopra\.com\/js\/woopra\.js/i, // Chrome extensions /extensions\//i, /^chrome:\/\//i, /^chrome-extension:\/\//i, // Other plugins /127\.0\.0\.1:4001\/isrunning/i, // Cacaoweb /webappstoolbarba\.texthelp\.com\//i, /metrics\.itunes\.apple\.com\.edgesuite\.net\//i, ], }; ``` ## [Sampling Data](https://docs.sentry.io/platforms/javascript/legacy-sdk/tips.md#sampling-data) It happens frequently that errors sent from your frontend can be overwhelming. One solution here is to only send a sample of the events that happen. You can do this via the `shouldSendCallback` setting: ```javascript shouldSendCallback: function(data) { // only send 10% of errors var sampleRate = 10; return (Math.random() * 100 <= sampleRate); } ``` ## [jQuery AJAX Error Reporting](https://docs.sentry.io/platforms/javascript/legacy-sdk/tips.md#jquery-ajax-error-reporting) For automatically reporting AJAX errors from jQuery, the following tips might be helpful, however depending on the type of request you might have to do slightly different things. ## [Same Origin](https://docs.sentry.io/platforms/javascript/legacy-sdk/tips.md#same-origin) Whenever an Ajax request completes with an error, jQuery triggers the `ajaxError` event, passing the `event` object, the `jqXHR` object (prior to jQuery 1.5, the `XHR` object), and the `settings` object that was used in the creation of the request. When an HTTP error occurs, the fourth argument (`thrownError`) receives the textual portion of the HTTP status, such as “Not Found” or “Internal Server Error.” You can use this event to globally handle Ajax errors: ```javascript $(document).ajaxError(function (event, jqXHR, ajaxSettings, thrownError) { Raven.captureMessage(thrownError || jqXHR.statusText, { extra: { type: ajaxSettings.type, url: ajaxSettings.url, data: ajaxSettings.data, status: jqXHR.status, error: thrownError || jqXHR.statusText, response: jqXHR.responseText.substring(0, 100), }, }); }); ``` ##### Note * This handler is not called for cross-domain script and cross-domain JSONP requests. * If `$.ajax()` or `$.ajaxSetup()` is called with the `global` option set to `false`, the `.ajaxError()` method will not fire. * As of jQuery 1.8, the `.ajaxError()` method should only be attached to document. ## [Cross Origin](https://docs.sentry.io/platforms/javascript/legacy-sdk/tips.md#cross-origin) Due to security reasons most web browsers are not giving permissions to access error messages for cross domain scripts. This is not jQuery issue but an overall JavaScript limitation. Depending on your situation you have different options now: ### [When you control the backend](https://docs.sentry.io/platforms/javascript/legacy-sdk/tips.md#when-you-control-the-backend) If you have access to the backend system you are calling, you can set response headers to allow a cross domain call: ```yaml Access-Control-Allow-Origin: * ``` Script tags have now got a new non-standard attribute called `crossorigin` ([read more](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#attr-crossorigin)). The most secure value for this would be `anonymous`. So, you’ll have to modify your script tags to look like the following: ```html ``` ### [When you have no access to the backend](https://docs.sentry.io/platforms/javascript/legacy-sdk/tips.md#when-you-have-no-access-to-the-backend) If you have no access to the backend, you could try a workaround, which is basically adding a timeout on the Ajax call. This is however very dirty, and will fail on slow connection or long response time: ```javascript $.ajax({ url: 'http://mysite/leaflet.js', success: function() { ... }, error: function() { ... }, timeout: 2000, // 2 seconds timeout before error function will be called dataType: 'script', crossDomain: true }); ``` ## [Raven Test Kit](https://docs.sentry.io/platforms/javascript/legacy-sdk/tips.md#raven-test-kit) When building tests for your application, you want to assert that the right flow-tracking or error is being sent to *Sentry*, **but** without really sending it to the *Sentry* system. This way you won’t swamp it with false reports during test running and other CI operations. [Raven Test Kit](https://github.com/wix/raven-testkit) enables Raven to work natively in your application, but it overrides the default Raven transport mechanism so the report is not really sent but rather logged locally. In this way, the logged reports can be fetched later for usage verification or other uses you may have in your testing environment. ### [Installation](https://docs.sentry.io/platforms/javascript/legacy-sdk/tips.md#installation) ```shell npm install raven-testkit --save-dev ``` ### [How to Use](https://docs.sentry.io/platforms/javascript/legacy-sdk/tips.md#how-to-use) Then you may create a `testkit` instance and validate your reports against it as follows: ```javascript import testKitInitializer from "raven-testkit"; const testKit = testKitInitializer(Raven); // any scenario that should call Raven.catchException(...) expect(testKit.reports()).to.have.lengthOf(1); const report = testKit.reports()[0]; expect(report).to.have.property("release").to.equal("test"); ``` Additionally, you may pass your own `shouldSendCallback` logic ```javascript const shouldSendCallback = (data) => { return; /* your own logic */ }; const testKit = testKitInitializer(Raven, shouldSendCallback); ``` Other useful API, more example usage and updates can be found in [Raven Test Kit](https://github.com/wix/raven-testkit)