Does JavaScript support interfaces like those in Java?

General Discussions
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3

Totally agree with @dimplesaini.230. I’ve used that approach myself, but in bigger codebases, you often want some validation at runtime too. I usually add a manual method checker to make sure the object really fits the javascript interface expectations:

function implementsInterface(obj, methods) {
  return methods.every(method => typeof obj[method] === 'function');
}

const listener = {
  onEvent: function(evt) { console.log(evt); }
};

if (implementsInterface(listener, ['onEvent'])) {
  listener.onEvent('Hello!');
} else {
  throw new Error('Object does not implement required interface');
}

Still not bulletproof, but it gives you an extra safety net, especially when onboarding new devs or working on large, modular systems.