# TypeError: Cannot read properties of undefined (reading 'Mode')

**URL:** <https://pdfjs.community/t/typeerror-cannot-read-properties-of-undefined-reading-mode/1988>\
**Category:** Technical Support\
**Created:** [August 27, 2022, 6:32pm UTC](https://pdfjs.community/t/typeerror-cannot-read-properties-of-undefined-reading-mode/1988 "2022-08-27T18:32:04Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![system](https://canada1.discourse-cdn.com/flex031/uploads/pdfjscommunity/original/1X/ffbcd25c7d423db8d5acd5db201c272f4db306dd.png) [@system](https://pdfjs.community/u/system)\
**Post date:** [August 27, 2022, 6:32pm UTC](https://pdfjs.community/t/typeerror-cannot-read-properties-of-undefined-reading-mode/1988/3 "2022-08-27T18:32:09Z")

</div>

**Hello, I’m Ron, an automated tech support bot 🤖**

While you wait for one of our customer support representatives to get back to you, please check out some of these documentation pages:

Guides:
- [Core engine for WebViewer - Creating your own UI using WebViewer Core](https://pdfjs.express/documentation/ui-customization/core#creating-your-own-ui-using-webviewer-core)
- [Default UI for WebViewer - How it works behind the scenes](https://pdfjs.express/documentation/ui-customization/default-ui#how-it-works-behind-the-scenes)
- [Rich text](https://pdfjs.express/documentation/annotation/rich-text.8)

APIs:
- [UndefinedsearchInProgress](https://pdfjs.express/api/namespaces.list.html#event:searchInProgress__anchor)
- [Core.DisplayMode - new DisplayMode(docViewer, mode [, scrollable])](https://pdfjs.express/api/Core.DisplayMode.html#DisplayMode__anchor)
- [Core.Tools.MarqueeZoomTool - new MarqueeZoomTool(docViewer)](https://pdfjs.express/api/Core.Tools.MarqueeZoomTool.html#MarqueeZoomTool__anchor)

Forums:
- [Search a keyword and annotate it programmatically](https://pdfjs.community/t/search-a-keyword-and-annotate-it-programmatically/691/4)
- [PDF is displayed without previous annotations](https://pdfjs.community/t/pdf-is-displayed-without-previous-annotations/1738/1)
- [Error when loading base64 document](https://pdfjs.community/t/error-when-loading-base64-document/1577/1)

  
  

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