Why does script error keep coming up

Settings on your computer or within your network may have been adjusted to block things like Java Applets or Active X controls. Changing the settings, if allowable, may relieve the problem. A script error is often a nuisance rather than a serious problem. Certain operating systems or browsers may have glitches of their own or may be in need of updates. Problems can also occur if hardware is outdated or corrupted. Make sure your drivers are up to date as well.

If you continue seeing the same script error, or others, obviously more troubleshooting is required. What we wrote above applies to the latest browser, or more specifically to:. Firefox has different behavior for runtime errors. These will be provided to the onerror callback without any obfuscation, even if the script is served from a different origin.

Syntax errors will be blocked though if the CORS headers are missing. Internet Explorer 10 and below will report all available data for errors. This is now considered a security risk. Real user monitoring tools such as Sematext Experience , can help you detect script errors by logging them to a remote server. RUM tools that have error tracking will report such errors as they happen to real users on your website.

When error tracking tools report errors, they usually report a detailed stack trace and error message which helps the developer track down the issue in their code.

But as explained earlier, this special kind of error will be missing this additional information. You can avoid this by following the instructions above to adjust the script tag and the servers from which the script is served. Script Error is a special kind of error that you get when a runtime or syntax error occurs in a script that is served from a different domain, subdomain, or port.

To even detect such errors you need a good monitoring solution. You could go for a real user monitoring solution such as Sematext Experience or a front-end monitoring tool that features RUM, logging, and synthetic monitoring that gives you end-to-end visibility into your application performance, in which case, Sematext Cloud is the tools for you.

If you have already detected such errors with your RUM tools and you are wondering why the stack trace or message is missing, you should follow the instructions above to adjust the script tag or the server from where the files are served. This is appropriate for a CDN where the script may be requested by any third-party domain. If this is a private host for a known set of domains, you can provide that list in place of the wildcard, for instance:.

You need to implement the Access-Control-Allow-Origin response header on the third-party server where the external script is coming from. How and where to add the HTTP header depends on the type of the third-party server.

For example, here is a code example you can use on an Apache server. You can add it to the. It enables the third-party server to send all files using the. After adding CORS support to the server, the Access-Control-Allow-Origin header appears in the response, the third-party script loads correctly, and the error message disappears from the console:.

It shares code examples and implementations for several different platforms such as IIS, Nginx, Tomcat, and others. Using a web proxy is an alternative method you can use to get around the problem. You need to set up a proxy on your web server, then make your Ajax requests, not to the third-party domain, but to the web proxy hosted on the same domain.

The proxy server forwards the request to the third-party server, fetches the script, and sends it back to your website. Thus, the browser interprets it as a same-origin request and allows your frontend code to access the third-party script. The web proxy, in fact, functions as an intermediary for your requests from other servers. There are some open-source CORS proxies available on the web, such as crossorigin. However, these services should be only used in development. Never use an open CORS proxy on a production site, they are unreliable and may pose serious security risks.

Depending on what browser your users are running, the above properties may or may not have an effect. This sums up the situation as of writing, regarding browser support for the crossorigin attribute and CORS:.

In these browsers, if the script tag is present, the HTTP header needs to be also present. Otherwise, the script will be blocked.