Function isPromise

packages/core/src/util/lang.ts:14–18

(obj: any)

 * Determine if the argument is shaped like a Promise
 */
export function isPromise<T = any>(obj: any): obj is Promise<T> {
  // allow any Promise/A+ compliant thenable.
  // It's up to the caller to ensure that obj.then conforms to the spec
  return !!obj && typeof obj.then === 'function';
}

/**
 * Determine if the argument is a Subscribable