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Dynamically Change Exposed Variables in Electron Preload Scripts

Learn how to dynamically adjust what is exposed in your Electron preload scripts based on navigation events, optimizing your app's performance and functionality. --- This video is based on the question https://stackoverflow.com/q/67083607/ asked by the user 'pushkin' ( https://stackoverflow.com/u/3479456/ ) and on the answer https://stackoverflow.com/a/67084204/ provided by the user 'pushkin' ( https://stackoverflow.com/u/3479456/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How to dynamically change what's exposed in a preload script? Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Dynamically Change Exposed Variables in Electron Preload Scripts When developing applications using Electron, one common requirement is to dynamically adjust what is exposed in your preload scripts based on the pages being loaded. This need arises particularly in situations where your app can navigate between different pages, each requiring its own set of variables or functions. In this guide, we'll explore how to achieve this dynamic behavior effectively. The Problem Imagine you have a BrowserWindow with a preload script attached. This script is initially set to expose certain functions or variables when page A is loaded. However, when the application navigates to page B, you want to have different functions or variables available. The challenge here is how to detect when navigation occurs and how to adjust the exposed content in the preload script accordingly. You might consider passing additional arguments to the preload script, like so: [[See Video to Reveal this Text or Code Snippet]] However, this approach has a limitation: if page A is loaded first, the variable indicating that you are on page B will be false, and this state will persist even when you navigate to page B later. Thus, we need a solution that allows for real-time updates based on page navigation. The Solution Fortunately, there is a relatively straightforward solution. According to Electron developers, preload scripts get re-executed with every navigation. This means you can utilize JavaScript's location.href property within your preload script to determine which page is currently being displayed. Steps to Implement Dynamic Page Detection Utilize location.href in the Preload Script: In your preload script, you can easily check the current URL using: [[See Video to Reveal this Text or Code Snippet]] Based on the value of currentPage, you can decide what functions or variables to expose. Example of Conditional Exposition: Here’s a simple example that demonstrates how you can expose different functions based on the current page: [[See Video to Reveal this Text or Code Snippet]] Implementing Navigation Tracking: While the above steps help in exposing the right methods, real-time tracking when the page changes can be done via the ipcMain and ipcRenderer communication in Electron. Set up an event listener in your main process to track navigations and send corresponding data to the preload script when necessary. Using ipcRenderer: Your preload script can listen for messages from the main process to adjust its state. Here’s a rudimentary way to set that up: In your main process: [[See Video to Reveal this Text or Code Snippet]] In your preload script: [[See Video to Reveal this Text or Code Snippet]] Conclusion By understanding how Electron handles preload scripts and their re-execution on navigation, you can create a dynamic and responsive preload environment. The key takeaway is to leverage the location.href property and use IPC communication to better manage updates. This approach ensures that your application remains flexible and performs optimally, providing users with the intended functionalities regardless of navigations. Efficient usage of preload scripts can enhance your Electron app's interactivity and maintainability. So go ahead, implement these methods, and create a richer user experience in your Electron applications!