Relative Paths in Javascript in an external file

javascript

relative-paths

absolute-paths

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byAnton Shumikhin·Jan 9, 2025

Employ document.currentScript.src, capturing the script's absolute URL. Subsequently, shape your relative paths using the URL() constructor. This method retains its accuracy even with external JavaScript files.

// This goes in your external .js file
let scriptPath = document.currentScript.src; // "Ask me what you shall, I've got your path covered!"
let relativePath = new URL('../path/to/resource', scriptPath).href; // "Know your ways around, do ya?"

// Now, you use relativePath when necessary
document.querySelector('#resource').src = relativePath; // "Pointing you to the right direction!"

Here, scriptPath fetches the script's location, and relativePath accordingly adjusts the path to resources, ensuring they operate relative to the script's present directory.

Effective use of absolute and base URLs

Relative paths are handy for their dynamic nature but can cause confusion in projects having a complex folder structure. To counteract this, consider using absolute paths or defining a base URL. For example, if you have a set of images used throughout your app, defining them as CSS background images is a cleaner solution than dealing with JavaScript's src attribute.

Expert's Tip: In an ASP.NET environment, the @Url.Content method can be utilized to define a base path as a global variable. This method allows comprehensive access throughout your JavaScript files.

Ensuring path compatibility between development and production

Bear in mind that your local development setup and production servers may have different folder structures and virtual directories. These differences can impact how your paths get resolved. Therefore, consistently practice the following habits:

Declare base paths in your layout's script element.
Manage images predominantly using CSS.
Test your paths thoroughly on their target server environments.

Streamline management of images

Instead of toggling with paths in JavaScript, let CSS take charge of image management, thereby keeping your JavaScript free for crafting dynamic functionality. This split will streamline your codebase and make it more maintainable.

Dynamically adjusting paths at runtime

Under certain circumstances, your web app might need to determine and adjust paths at runtime. jQuery provides utilities to determine the location of the script file at runtime and lets you adjust paths accordingly:

let scriptFolder = $('script[src*=external]').attr('src').replace('external.js', ''); // "Who moved my cheese?"

This nifty snippet finds the external.js file, extracts its folder path, and lets you dynamically assemble resource URLs. Valuable for complex applications!

Future-proofing and bonus tips

Unforeseen scenarios are a staple in development. Perhaps, browser cache or script execution order could impact your relative paths. For scenarios like these:

Set a <base> tag in your application: this creates a base for all relative URLs.
Modern build tools like Webpack or npm scripts can significantly simplify path management. They reduce manual errors and usually come with production-ready solutions out of the box. Remember: work smart, not hard!