The Text Expander JS plugin allows users to create and utilize custom text shortcuts that trigger JavaScript scripts, generating dynamic text replacements. These shortcuts can be typed directly into notes or triggered through buttons and links. The plugin supports complex configurations, such as parameterized shortcuts, regex-based matching, and integration with custom scripts. It works seamlessly with both modern and legacy editors in Obsidian, including mobile platforms. Advanced users can define shortcuts in organized files for better management and sharing. Additional features include creating custom popup boxes for user input, running external scripts, and supporting helper functions for more advanced automation.