The Object.observe() method was used for asynchronously observing the changes to an object. It provided a stream of changes in the order in which they occur. However, this API has been deprecated and removed from browsers. You can use the more general Proxy object instead.
The goal of ParallelArray was to enable data-parallelism in web applications. The higher-order functions available on ParallelArray attempted to execute in parallel, though they may fall back to sequential execution if necessary. To ensure that your code executes in parallel, it is suggested that the functions should be limited to the parallelizable subset of JS that Firefox supports.
The Promise.resolve(value) method returns a Promise object that is resolved with the given value. If the value is a thenable (i.e. has a "then" method), the returned promise will "follow" that thenable, adopting its eventual state; otherwise the returned promise will be fulfilled with the value.