getResourceState()

getResourceState() returns the current state of a resource — whether it is loading, has loaded, or is not loaded.

Signature

ResourceLoader.getResourceState(url: string): 'loading' | 'loaded' | 'unloaded'

Parameters

Parameter	Type	Description
url	string	The URL to query

Return Value

One of three string literals:

State	Meaning
'loading'	include() has been called for this URL and it has not yet finished
'loaded'	The resource has finished loading successfully
'unloaded'	The resource has never been loaded, was cancelled, errored out, or was explicitly unloaded

Note

getResourceState() returns 'unloaded' for URLs that the library has never seen. It never returns undefined.

---

State Transitions

[never seen / initial]
        │
        ▼
   'unloaded'  ◄────── cancelResource() / unloadResource() / error
        │
   include() called
        │
        ▼
   'loading'
        │
   load complete
        │
        ▼
    'loaded'

---

Examples

Check State After Loading

const url = 'https://cdn.example.com/app.js';

console.log(ResourceLoader.getResourceState(url)); // 'unloaded'

await ResourceLoader.include([url]);

console.log(ResourceLoader.getResourceState(url)); // 'loaded'

Conditional Load (Avoid Duplicate Loads)

async function ensureLoaded(url) {
  const state = ResourceLoader.getResourceState(url);

  if (state === 'loaded') {
    return; // Already loaded — nothing to do
  }

  if (state === 'loading') {
    // Wait for the in-flight load to complete
    // (call include() again — it returns the same Promise if already in flight)
    await ResourceLoader.include([url]);
    return;
  }

  // State is 'unloaded' — load it now
  await ResourceLoader.include([url]);
}

await ensureLoaded('https://cdn.example.com/charts.js');
renderChart(); // Safe to call — charts.js is definitely loaded

Debug: Log All Known Resource States

const urls = [
  'https://cdn.example.com/app.css',
  'https://cdn.example.com/app.js',
  'https://api.example.com/config.json',
];

urls.forEach(url => {
  console.log(`${url}: ${ResourceLoader.getResourceState(url)}`);
});

Guard Against Premature Usage

function renderWidget() {
  const chartUrl = 'https://cdn.example.com/charts.js';

  if (ResourceLoader.getResourceState(chartUrl) !== 'loaded') {
    console.error('Charts library is not loaded yet. Call loadDependencies() first.');
    return;
  }

  // Safe to use the charts API
  new Chart(/* ... */);
}

---

Notes

• getResourceState() is synchronous — it reads from an in-memory map and returns immediately.
• The state reflects what ResourceLoader.js knows about a URL. If a resource was added to the DOM outside of ResourceLoader.js (e.g., a <script> tag written directly in HTML), its state is still 'unloaded' from the library’s perspective.