Documentation

This function initialises a new JS runtime and performs the given computation within this context.

For example, we can evaluate an expression:

quickjs $ do
  res <- eval "1+2"
  liftIO $ print res

Declare a function and call it on an argument:

quickjs $ do
  _ <- eval_ "f = (x) => x+1"
  res <- eval "f(2)"
  liftIO $ print res

Pass a Haskell value to the JS runtime:

quickjs $ do
  _ <- eval_ "f = (x) => x+1"
  res <- withJSValue (3::Int) $ \x -> call "f" [x]
  liftIO $ print res

This env differs from regular quickjs, in that it wraps the computation in the runInBoundThread function. This is needed when running the Haskell program mutithreaded (e.g. when using the testing framework Tasty), since quickjs does not like being called from an OS thread other than the one it was started in. Because Haskell uses lightweight threads, this might happen if threaded mode is enabled, as is the case in Tasty. This problem does not occur when running via Main.hs, if compiled as single threaded... For more info see the paper Extending the Haskell Foreign Function Interface with Concurrency

Evaluates the given string and returns a Value (if the result can be converted).

More efficient than eval if we don't care about the value of the expression, e.g. if we are evaluating a function definition or performing other side-effects such as printing to console/modifying state.

Takes a value with a defined ToJSON instance. This value is marshalled to a JSValue and passed as an argument to the callback function, provided as the second argument to withJSValue