# Uncaught ReferenceError: localJsonpCallback is not defined using zoom web sdk

**URL:** <https://devforum.zoom.us/t/uncaught-referenceerror-localjsonpcallback-is-not-defined-using-zoom-web-sdk/20640>\
**Category:** Web\
**Created:** [June 8, 2020, 11:51am UTC](https://devforum.zoom.us/t/uncaught-referenceerror-localjsonpcallback-is-not-defined-using-zoom-web-sdk/20640 "2020-06-08T11:51:20Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![tommy](https://sea2.discourse-cdn.com/flex016/user_avatar/devforum.zoom.us/tommy/32/72769_2.png) [@tommy](https://devforum.zoom.us/u/tommy)\
**Post date:** [June 12, 2020, 8:38pm UTC](https://devforum.zoom.us/t/uncaught-referenceerror-localjsonpcallback-is-not-defined-using-zoom-web-sdk/20640/2 "2020-06-12T20:38:40Z")

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Hey @rahul4,

Make sure you allow time for the [Web SDK files](https://marketplace.zoom.us/docs/sdk/native-sdks/web/getting-started/integrate) to load before joining a meeting.

```auto
ZoomMtg.preLoadWasm();
ZoomMtg.prepareJssdk();

```

You can check the network tab to see if you are joining the meeting before the Web Assembly files have loaded.

Thanks,  
Tommy

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