Hi @JavanMRLab, what is probably happening is that any changes you make to your JS scripts are overwritten by Builder when you sync your files with Pavlovia, because the default settings in Builder will export the JS and html when you click the sync button (thus overwriting your changes). If you wanted to only export the JS manually (i.e., not when you save or sync), you can make these changes in the Export html drop down list in the Online tab of experiment settings. However, I think you would be better off using a code component if you want to add JS code to your experiment: