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    <title>article RUM JavaScript Agent gives JavaScript error on Browser API JS functions in Troubleshooting</title>
    <link>https://community.dynatrace.com/t5/Troubleshooting/RUM-JavaScript-Agent-gives-JavaScript-error-on-Browser-API-JS/ta-p/305133</link>
    <description>&lt;DIV class="lia-message-template-content-zone"&gt;
&lt;H2&gt;Summary&lt;/H2&gt;
&lt;P&gt;Applications monitored by RUM generate JavaScript errors referring after New RUM Experience is enabled. This is caused by the RUM JavaScript Agent interacting with code that implements as standard browser API incorrectly in other JavaScript on the page.&lt;/P&gt;
&lt;H2&gt;Problem&lt;/H2&gt;
&lt;P&gt;&amp;nbsp;&lt;/P&gt;
&lt;P&gt;After enabling the New Real User Monitoring Experience, some customers have reported encountering JavaScript errors on pages that worked before the new experience was activated. We are seeing errors arise when the front-end code using common browser APIs that return an invalid value, i.e. a value that does not satisfy the testing function.&lt;/P&gt;
&lt;P&gt;The RUM JavaScript Agent uses many common Browser APIs that may also be used by JavaScript code in use elsewhere on the page. In order for full compatibility, all code that uses these Browser APIs must conform to the MSN specification for the function in question. If the spec is not followed, errors can occur when the RUM JS Agent tries to make use of that API.&lt;BR /&gt;The APIs that the RUM JS Agent relies on are &lt;A href="https://docs.dynatrace.com/javascriptapi/doc-latest/documents/RUM_JavaScript_Browser_API_Usage.html?_gl=1*1jbdp7m*_gcl_au*Mzg0OTAwMzYxLjE3OTAyNTk0Mjg.*_ga*MjE4NDE3ODAwLjE3NTk4Njg1NDk.*_ga_1MEMV02JXV*czE3OTEzODE1ODAkbzI5MCRnMSR0MTc5MTM4MjY2OSRqNTkkbDAkaDA.#browser-apis-used-by-dynatrace-rum-javascript" target="_self"&gt;listed here&lt;/A&gt; along with a links to the relevant specifications.&lt;/P&gt;
&lt;P&gt;&amp;nbsp;&lt;/P&gt;
&lt;H2&gt;Resolution&lt;/H2&gt;
&lt;P&gt;In order to resolve this issue, the other JavaScript code on the page must be modified so that it only returns valid values for this function.&lt;/P&gt;
&lt;P&gt;As a temporary solution, you can disable New Real User Monitoring in the application settings.&lt;BR /&gt;You can just keep Classic RUM enabled.&lt;/P&gt;
&lt;P&gt;Note: Reverting to Classic RUM will result in the loss of new monitoring for RUM data and no data in all third-generation applications, such as Experience Vitals.&lt;/P&gt;
&lt;P&gt;Recommandation: Please ensure that you implement browser APIs in your JavaScripts in accordance with specification standards, thus avoiding any potential issues with other tools that utilise these APIs, such as Dynatrace New RUM.&lt;/P&gt;
&lt;P&gt;&lt;EM&gt;&amp;nbsp;&lt;/EM&gt;&lt;/P&gt;
&lt;H2&gt;What's next&lt;/H2&gt;
&lt;P&gt;This issue arises because the New RUM agent introduced functionality that utilises Browser APIs that Classic RUM did not. Therefore, it relies on the correct implementation of these APIs used by other JavaScript on the same page. &lt;A href="https://docs.dynatrace.com/javascriptapi/doc-latest/documents/RUM_JavaScript_Browser_API_Usage.html?_gl=1*1jbdp7m*_gcl_au*Mzg0OTAwMzYxLjE3OTAyNTk0Mjg.*_ga*MjE4NDE3ODAwLjE3NTk4Njg1NDk.*_ga_1MEMV02JXV*czE3OTEzODE1ODAkbzI5MCRnMSR0MTc5MTM4MjY2OSRqNTkkbDAkaDA.#browser-apis-used-by-dynatrace-rum-javascript" target="_self"&gt;You can find a list of all the APIs that RUM interacts with on this page.&lt;/A&gt;&lt;/P&gt;
&lt;P&gt;The process of identifying all the APIs requiring adjustment implementation can be conducted by performing a health check, with the following steps (When new RUM is enabled):&lt;/P&gt;
&lt;OL&gt;
&lt;LI&gt;Open Chrome.&lt;/LI&gt;
&lt;LI&gt;Open Developer Tools (F12).&lt;/LI&gt;
&lt;LI&gt;Navigate to the affected web application.&lt;/LI&gt;
&lt;LI&gt;Open Console and run:&lt;/LI&gt;
&lt;/OL&gt;
&lt;LI-CODE lang="markup"&gt;await dynatrace.loadDebugTools();
dynatrace.debugtools.runHealthCheck();&lt;/LI-CODE&gt;
&lt;P&gt;&amp;nbsp;&lt;/P&gt;
&lt;P&gt;If this article did not help, please open a support ticket, mention that this article was used and provide the following in the ticket:&lt;/P&gt;
&lt;P&gt;Link to the RUM Application in your Environment&lt;BR /&gt;Link to the JavaScript Error in your Environment&lt;BR /&gt;A .HAR file of a page where the problem occurs&lt;/P&gt;
&lt;H2&gt;&lt;BR /&gt;Related reading&lt;/H2&gt;
&lt;P&gt;&lt;EM&gt;*Link this article to other relevant configuration or troubleshooting guides, including any applicable troubleshooting maps.&lt;BR /&gt;&lt;span class="lia-unicode-emoji" title=":open_book:"&gt;📖&lt;/span&gt; &lt;A id="link_6" class="page-link lia-link-navigation lia-custom-event" href="https://community.dynatrace.com/t5/Troubleshooting/RUM-JavaScript-Agent-gives-a-not-iterable-error-on-Symbol/ta-p/293792" target="_self"&gt;RUM JavaScript Agent gives a 'not iterable error' on Symbol.iterator&lt;/A&gt;&lt;/EM&gt;&lt;/P&gt;
&lt;/DIV&gt;</description>
    <pubDate>Thu, 08 Oct 2026 14:35:30 GMT</pubDate>
    <dc:creator>Bill_Emerson</dc:creator>
    <dc:date>2026-10-08T14:35:30Z</dc:date>
    <item>
      <title>RUM JavaScript Agent gives JavaScript error on Browser API JS functions</title>
      <link>https://community.dynatrace.com/t5/Troubleshooting/RUM-JavaScript-Agent-gives-JavaScript-error-on-Browser-API-JS/ta-p/305133</link>
      <description>&lt;P&gt;&lt;LI-TOC indent="15" liststyle="disc" maxheadinglevel="2"&gt;&lt;/LI-TOC&gt;&lt;/P&gt;
&lt;DIV class="lia-message-template-content-zone"&gt;
&lt;P&gt;*&lt;EM&gt;Use a table of contents for longer articles.&amp;nbsp;&lt;/EM&gt;&lt;/P&gt;
&lt;H2&gt;Summary&lt;/H2&gt;
&lt;P&gt;&lt;EM&gt;*This is a mandatory section.&lt;/EM&gt;&lt;/P&gt;
&lt;P&gt;&lt;EM&gt;Short description of which part of the Dynatrace platform the article refers to and what kind of problem it will help resolve/ task it will describe.&lt;/EM&gt;&lt;/P&gt;
&lt;P&gt;&amp;nbsp;&lt;/P&gt;
&lt;H2&gt;Problem&lt;/H2&gt;
&lt;P&gt;&lt;EM&gt;*This is a mandatory section.&lt;/EM&gt;&lt;/P&gt;
&lt;P&gt;&lt;EM&gt;Provide a precise description of the problem/ task to be described. Use anonymized screenshots, and include text for&amp;nbsp;important messages, errors, or information that will help the customer find this article when searching.&lt;/EM&gt;&lt;/P&gt;
&lt;P&gt;&amp;nbsp;&lt;/P&gt;
&lt;H2&gt;Troubleshooting steps&lt;/H2&gt;
&lt;P&gt;&lt;EM&gt;*This section can be omitted as necessary.&lt;/EM&gt;&lt;/P&gt;
&lt;P&gt;&lt;EM&gt;Explain what troubleshooting steps should be taken to ensure the problem matches this article.&lt;/EM&gt;&lt;/P&gt;
&lt;P&gt;&amp;nbsp;&lt;/P&gt;
&lt;H2&gt;Resolution&lt;/H2&gt;
&lt;P&gt;&lt;EM&gt;*This section can be omitted for articles that guide customers on case creation.&lt;/EM&gt;&lt;/P&gt;
&lt;P&gt;&lt;EM&gt;Explain the solution or all possible solutions resulting from the troubleshooting steps.&lt;BR /&gt;&lt;BR /&gt;&lt;/EM&gt;&lt;/P&gt;
&lt;H2&gt;What's next&lt;/H2&gt;
&lt;P&gt;&lt;EM&gt;*This is a mandatory section. Customers need a way to respond or follow up if they have questions.&amp;nbsp;&lt;/EM&gt;&lt;/P&gt;
&lt;P&gt;&lt;EM&gt;Explain what to do if the article didn't help.&amp;nbsp;&lt;/EM&gt;&lt;EM&gt;Note that there are multiple options available, including:&lt;/EM&gt;&lt;/P&gt;
&lt;OL&gt;
&lt;LI&gt;&lt;EM&gt;&lt;STRONG&gt;Opening a chat or support case&amp;nbsp;&lt;/STRONG&gt;- be as specific as possible about the information the customer should include in the case.&amp;nbsp;&lt;/EM&gt;&lt;EM&gt;Use the following formula and fill or change the bullet points:&lt;BR /&gt;&lt;BR /&gt;&lt;/EM&gt; If this article didn't help, &lt;STRONG&gt;create a chat or open a support case&lt;/STRONG&gt;
&lt;UL&gt;
&lt;LI&gt;Mention that you reviewed this article.&lt;/LI&gt;
&lt;LI&gt;Include the following details:
&lt;UL&gt;
&lt;LI&gt;Link to XYZ&lt;/LI&gt;
&lt;LI&gt;Screenshot of XYZ&lt;/LI&gt;
&lt;LI&gt;Information about XYZ&lt;/LI&gt;
&lt;/UL&gt;
&lt;/LI&gt;
&lt;/UL&gt;
&lt;/LI&gt;
&lt;LI&gt;&lt;EM&gt;&lt;STRONG&gt;Suggesting Product Idea&lt;/STRONG&gt; - encourage the customer to suggest/ vote for a Product Idea explaining their business use case.&lt;BR /&gt;&lt;/EM&gt;
&lt;DIV&gt;Please submit a Product Idea with detailed information about your request and use case in the Product Ideas forum. Our Product Management team regularly reviews these suggestions:&lt;/DIV&gt;
&lt;A href="https://community.dynatrace.com/t5/Dynatrace-product-ideas/idb-p/DynatraceProductIdeas" target="_blank" rel="noopener"&gt;https://community.dynatrace.com/t5/Dynatrace-product-ideas/idb-p/DynatraceProductIdeas&lt;/A&gt;&lt;/LI&gt;
&lt;LI&gt;&lt;STRONG&gt;&lt;EM&gt;Explain this will change in the future &lt;/EM&gt;&lt;/STRONG&gt;&lt;EM&gt;- explain that this behavior will change in a future release. (No product idea / support case needed)&lt;/EM&gt;&lt;/LI&gt;
&lt;LI&gt;&lt;STRONG&gt;&lt;EM&gt;Alternatives -&lt;/EM&gt;&lt;/STRONG&gt;&lt;EM&gt;&amp;nbsp;any other actions or links to other articles that could move the customer forward.&lt;/EM&gt;&lt;/LI&gt;
&lt;/OL&gt;
&lt;H2&gt;&lt;BR /&gt;Related reading&lt;/H2&gt;
&lt;P&gt;&lt;EM&gt;*Link this article to other relevant configuration or troubleshooting guides, including any applicable troubleshooting maps.&lt;BR /&gt;:open_book:&amp;nbsp;&amp;nbsp;&lt;/EM&gt;&lt;A href="https://community.dynatrace.com/t5/Troubleshooting/" target="_blank" rel="noopener"&gt;XXX Troubleshooting Map&lt;/A&gt;&lt;/P&gt;
&lt;P&gt;:open_book:&amp;nbsp; Link 1&lt;/P&gt;
&lt;P&gt;:open_book:&amp;nbsp; Link 2&lt;/P&gt;
&lt;P&gt;:open_book:&amp;nbsp; Link 3&lt;/P&gt;
&lt;P&gt;:open_book:&amp;nbsp; Link 4&lt;/P&gt;
&lt;/DIV&gt;</description>
      <pubDate>Thu, 08 Oct 2026 14:35:30 GMT</pubDate>
      <guid>https://community.dynatrace.com/t5/Troubleshooting/RUM-JavaScript-Agent-gives-JavaScript-error-on-Browser-API-JS/ta-p/305133</guid>
      <dc:creator>Bill_Emerson</dc:creator>
      <dc:date>2026-10-08T14:35:30Z</dc:date>
    </item>
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