The "@flownet/lib-load-browser-script-url" project is essentially a JavaScript library aimed to dynamically load external scripts into a browser environment.
This piece of code provides a mechanism for loading and managing JavaScript resources in an HTML-based application dynamically. It generates a promise-based function, which allows asynchronous handling and offers a pipeline for error or success events.
The essence of this project's functionality is the ability to dynamically load a script from a provided URL. This might be useful in cases where applications might need to load scripts based on certain actions or conditions that arise during the runtime.
Another central aspect is the script tag management functionality. The function checks whether a script with a given ID already exists in a document and creates a new script tag if it doesn't. This efficiently avoids unnecessary duplications of the same script.
The script also includes robust error handling capabilities. It validates the input parameters and provides user-friendly error messages if invalid inputs are given. Also, it listens for error events that occur while loading the script. If such an event occurs, the function rejects the promise with the reason for the error.
The project has built-in event handling abilities. When a script is successfully loaded, an 'onload' event is dispatched, and the promise is resolved. The original 'onload' event is retained and fired alongside the newly attached event.
The function also facilitates script tag attribute management, allowing the end-user to determine whether the script should be executed asynchronously with the 'async' attribute or deferred until the page has finished parsing with the 'defer' attribute. It also allows the addition of arbitrary attributes to the script tag.
After all the setup, the function then assigns the script source and appends the script tag to the document head. This allows the browser to load and execute the script in the context of the currently loaded document.