fallbackURLer

fallbackURLer is a lightweight, open‑source JavaScript utility designed to simplify the handling of alternative or fallback URLs for web applications. Developed in 2019 by a group of front‑end engineers, the library addresses the common need to redirect users to secondary resources when a primary link is unavailable, broken, or blocked by network or policy restrictions.

The core functionality of fallbackURLer is provided by a set of functions that validate a given URL, attempt to access it via a fetch or XMLHttpRequest, and, upon failure, automatically switch to an alternative address. The API is intentionally minimal: developers provide a primary URL, a fallback URL, and an optional timeout threshold. The library returns a promise that resolves with the first successful response, preserving the original request semantics. In addition to simple checks, fallbackURLer can be configured to handle error codes, timeouts, and network status changes, enabling more resilient user experiences.

fallbackURLer is distributed under the MIT license and is compatible with modern browsers as well as Node.js environments. The library’s source code is hosted on GitHub and includes comprehensive tests written with Jest. The project has a modest but steady user base, with usage spanning content delivery networks, progressive web apps, and single‑page applications that require graceful degradation.

In typical usage, fallbackURLer is imported as a module, and a developer calls the `attempt` function with the URLs of interest. The promise returned by `attempt` resolves with the response object of the first URL that succeeds, allowing developers to seamlessly continue processing without exposing failures to users. Because the logic is encapsulated in a single file, it can be easily bundled with other assets, and developers appreciate its small footprint of under 5 kilobytes when minified.

While fallbackURLer is not a replacement for comprehensive network error handling libraries, it serves as a specialized tool for developers who only need to manage alternate link resolution efficiently and declaratively.