OrchardCMS/OrchardCore · error · TypeError

Super expression must either be null or a function

Error message

Super expression must either be null or a function

What it means

Babel's _inherits helper throws this TypeError when class inheritance is compiled with a superclass that is neither a function nor null — i.e. the 'extends' expression did not evaluate to a constructor. Found in Font Awesome's bundled, transpiled fontawesome.js.

Solutions

1. Fix script load order so the superclass module/bundle loads before fontawesome.js
2. Resolve circular imports or undefined exports of the base class
3. Check for duplicate/conflicting versions of libraries defining the parent class
4. Verify the CDN/script tag wasn't blocked (404/ad-blocker) leaving the dependency undefined

Example fix

// before
class Icon extends SomeLibrary.Thing // SomeLibrary failed to load => undefined
// after
if (typeof SomeLibrary === 'undefined') { console.error('SomeLibrary must be loaded first'); } else { class Icon extends SomeLibrary.Thing {} }

if (typeof SuperClass !== 'function' && SuperClass !== null) throw new TypeError('Expected a constructor to extend');

function isConstructor(v) { return typeof v === 'function' && v.prototype?.constructor === v || typeof v === 'function'; }

try { initIcons(); } catch (e) { if (e instanceof TypeError && e.message.includes('Super expression')) console.error('A superclass bundle failed to load or export a class'); }

When it happens

Trigger: Compiled class code like class A extends B where B is undefined, an object, or a non-constructor value at the time _inherits(B) runs.

Common situations: Script load order problems so the base class isn't defined yet; circular imports leaving the superclass undefined; a minified/bundled dependency collision replacing a class with an object; broken UMD/global export from a CDN script failing to load first.

Understand the failure class

Background: "not installed", "pip install", "required for": how missing-dependency errors surface across open-source libraries — this error's family across 34 libraries.

Related errors

• @@toPrimitive must return a primitive value.
• @@toPrimitive must return a primitive value.
• @@toPrimitive must return a primitive value.
• Failed to load
• is missing the required "orchardBaseUrl" field.

AI-assisted analysis of OrchardCMS/OrchardCore@4306c0717f (2026-09-13). Data as JSON: /api/errors/6112a69934106169. Report an issue: GitHub.

Appendix: source

Thrown at src/OrchardCore.Modules/OrchardCore.Resources/wwwroot/Vendor/fontawesome-free-6.7.2/js/fontawesome.js:18

/*!
 * Font Awesome Free 6.7.2 by @fontawesome - https://fontawesome.com
 * License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License)
 * Copyright 2024 Fonticons, Inc.
 */
(function () {
  'use strict';

  function _defineProperty(e, r, t) {
    return (r = _toPropertyKey(r)) in e ? Object.defineProperty(e, r, {
      value: t,
      enumerable: !0,
      configurable: !0,
      writable: !0
    }) : e[r] = t, e;
  }
  function _inherits(t, e) {
    if ("function" != typeof e && null !== e) throw new TypeError("Super expression must either be null or a function");
    t.prototype = Object.create(e && e.prototype, {
      constructor: {
        value: t,
        writable: !0,
        configurable: !0
      }
    }), Object.defineProperty(t, "prototype", {
      writable: !1
    }), e && _setPrototypeOf(t, e);
  }
  function ownKeys(e, r) {
    var t = Object.keys(e);
    if (Object.getOwnPropertySymbols) {
      var o = Object.getOwnPropertySymbols(e);
      r && (o = o.filter(function (r) {
        return Object.getOwnPropertyDescriptor(e, r).enumerable;
      })), t.push.apply(t, o);
    }

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