Function parse 

pub fn parse(
    filename: String,
    source_text: String,
    options: Option<ParserOptions>,
) -> AsyncTask<ResolveTask>

Parse JS/TS source asynchronously on a separate thread.

Note that not all of the workload can happen on a separate thread. Parsing on Rust side does happen in a separate thread, but deserialization of the AST to JS objects has to happen on current thread. This synchronous deserialization work typically outweighs the asynchronous parsing by a factor of between 3 and 20.

i.e. the majority of the workload cannot be parallelized by using this method.

Generally parseSync is preferable to use as it does not have the overhead of spawning a thread. If you need to parallelize parsing multiple files, it is recommended to use worker threads.