japgolly.scalajs.react.callback

Pure asynchronous callback.

You can think of this as being similar to using Future - you can use it in for-comprehensions the same way - except AsyncCallback is pure and doesn't need an ExecutionContext.

When combining instances, it's good to know which methods are sequential and which are parallel (or at least concurrent).

The following methods are sequential:

• >>= / flatMap
• >> & <<
• flatTap

The following methods are effectively parallel:

• *> & <*()
• race
• zip & zipWith
• AsyncCallback.traverse et al

In order to actually run this, or get it into a shape in which in can be run, use one of the following:

• toCallback <-- most common
• asCallbackToFuture
• asCallbackToJsPromise
• unsafeToFuture
• unsafeToJsPromise

A good example is the Ajax 2 demo.

A callback with no return value. Equivalent to () => Unit.

Callback that can short-circuit along the way when conditions you specify, aren't met.

Especially useful for event handlers such as key handlers, drag-and-drop handlers, etc, where you check a condition, perform an effect, check another condition, perform another effect, etc.

This is meant to be lightweight, and be immediately useful without the typical pain of imports, implicit conversions and extension methods then normally accompany monad transforms in Scala.

For a more generic (i.e. beyond Option) or comprehensive monad transformer use Cats or similar.

A function to be executed later, usually by scalajs-react in response to some kind of event.

The purpose of this class is to lift effects into the type system, and use the compiler to ensure safety around callbacks (without depending on an external library like Cats).

() => Unit is replaced by Callback. Similarly, ReactEvent => Unit is replaced by ReactEvent => Callback.

Promise that is synchronous once its value has been set.