JavaScript Performance V8 vs Nashorn (for Typescript Language Service)

On the weekend I’ve worked on my API to interface with the Typescript language service from my Java code.

While the initial version I developed some months ago used the “tsserver” to communicate with the LanguageService I decided to rewrite that and to interface with the service directly (in memory or through an extra process).

For the in memory version I implemented 2 possible ways to load the JavaScript sources and call them

  • Nashorn
  • V8(with the help of j2v8)

I expected that Nashorn is slower than V8 already but after having implemented a small (none scientific) performance sample the numbers show that Nashorn is between 2 and 4 times slower than V8 (there’s only one call faster in Nashorn).

The sample code looks like this:

public static void main(String[] args) {
  try {
    executeTests(timeit("Boostrap", () -> new V8Dispatcher()));
    executeTests(timeit("Nashorn", () -> new NashornDispatcher()));
  } catch (Throwable e) {

private static void executeTests(Dispatcher dispatcher) throws Exception {
  timeit("Project", () -> dispatcher.sendSingleValueRequest(
    "LanguageService", "createProject", String.class, "MyProject").get());

  timeit("File", () -> dispatcher.sendSingleValueRequest(
    "LanguageService", "addFile", String.class, "p_0", DispatcherPerformance.class.getResource("sample.ts")).get());

  timeit("File", () -> dispatcher.sendSingleValueRequest(
    "LanguageService", "addFile", String.class, "p_0", DispatcherPerformance.class.getResource("sample2.ts")).get());

  timeit("Outline", () -> dispatcher.sendMultiValueRequest(
    "LanguageService", "getNavigationBarItems", NavigationBarItemPojo.class, "p_0", "f_0").get());

  timeit("Outline", () -> dispatcher.sendMultiValueRequest(
    "LanguageService", "getNavigationBarItems", NavigationBarItemPojo.class, "p_0", "f_1").get());

Provides the following numbers:

Boostrap : 386
Project : 72
File : 1
File : 0
Outline : 40
Outline : 10

Nashorn : 4061
Project : 45
File : 29
File : 2
Outline : 824
Outline : 39

The important numbers to compare are:

  • Bootstrap: ~400ms vs ~4000ms
  • 2nd Outline: ~10ms vs ~40ms

So performance indicates that the service should go with j2v8 but requiring that as hard dependency has the following disadvantages:

  • you need to ship different native binaries for each OS you want to run on
  • you need to ship v8 which might/or might not be a problem

So the strategy internally is that if j2v8 is available we’ll use v8, if not we fallback to the slower nashorn, a strategy I would recommend probably for your own projects as well.

If there are any Nashorn experts around who feel free to help me fix my implementation

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