You can use these API calls in your code if you need to, but I've actually found them quite useful when on the console in Chrome:
require.defined(moduleId) - returns true if your moduleId has been defined and is ready for use.
require.specified(moduleId) - returns true if your moduleId has been listed as a dependency by another defined module. Note that just because this returns true doesn't mean your moduleId is ready to use (don't you just love asynchrony?).
requirejs.s.contexts._.config - I learned about this from Vernon Kesner. This is technically a "back door/undocumented" call - so it could change or disappear without warning. However it returns a very useful object full of configuration info, see below:
Chrome Console results for requrejs.s.conects._.config
This is the result of calling requirejs.s.contexts._.config inside a sample gif-generation app I used to demo Web Workers at Devlink. You can see all the relevant configuration data: the base URL, the paths we've mapped, the shim configuration, etc.
Two other key items to know about when it comes to troubleshooting RequireJS are 'errbacks' and the requirejs.onError method:
When you make a require call, you can include a third argument - a callback that receives an error argument, allowing you to react to the error, instead of ultimately generating an uncaught exception. The method signature, when using "errbacks" looks like this:
require(
[ "backbone" ],
function ( Backbone ) {
return Backbone.View.extend({ /* your magic here */ });
},
function (err) {
/*
err has err.requireType (timeout, nodefine, scripterror)
and err.requireModules (an array of module Ids/paths)
Inside here you could requirejs.undef('backbone') to clear
the module from require locally - and you could even redefine
it here or fetch it from a different location (though the
fallback approach earlier takes care of this use-case more succinctly)
*/
}
);RequireJS has a global onError handler that will catch any errors not already handled by "errbacks". To use it, simply set it like this:
requirejs.onError = function (err) {
/*
err has the same info as the errback callback:
err.requireType & err.requireModules
*/
console.log(err.requireType);
// Be sure to rethrow if you don't want to
// blindly swallow exceptions here!!!
};