As JavaScript files grew, the old approach of adding another script tag to the page started to feel fragile. One file depended on another, a plugin needed jQuery first, custom code needed the plugin next and the order became something developers had to hold in their heads.
That might be manageable on a simple website. It becomes risky when the project has several behaviours and different pages need different scripts. One change to the script order can break an interface in a way that is not immediately obvious.
RequireJS was interesting because it addressed the organisation problem. It encouraged JavaScript to be split into modules with explicit dependencies, rather than relying entirely on global variables and script order.
Why Script Order Became A Problem
Script order bugs are frustrating because the code itself can look correct. The function exists in one file, the caller exists in another file and everything works until the files load in the wrong order. The dependency is real, but it is not clearly declared in the code.
As interfaces became more dynamic, that kind of hidden dependency became harder to tolerate. A project needed a better way to describe which parts of the code relied on which other parts.
define(['jquery'], function ($) {
function init() {
$('.menu-toggle').on('click', function () {
$('.menu').toggleClass('is-open');
});
}
return {
init: init
};
});Modules Made Ownership Clearer
The useful idea was not only asynchronous loading. It was the module boundary. A menu module could own menu behaviour. A gallery module could own gallery behaviour. Each one could declare its dependencies instead of assuming the page had already loaded everything in the correct order.
That changed the way JavaScript could be discussed. Instead of one growing file containing unrelated behaviour, the project could be broken into parts that matched the interface. That made later changes easier because the code had a clearer shape.
Production Still Needed Care
Loading many small files might be pleasant during development, but production performance still mattered. Too many requests could slow down the page, especially on mobile connections. That meant module loading needed to be paired with a build or optimisation step if the project grew.
RequireJS made the organisation problem visible. JavaScript was becoming too important to leave as a pile of ordered script tags.