Zone.waitFor(fn)

Zone.waitFor is a function that creates a callback that can be used with any async functionality. Calling Zone.waitFor registers a wait with the currently running request and returns a function that, when called, will decrement the wait count.

This is useful if there is async functionality other than what we implement. You might be using a library that has C++ bindings and doesn't go through the normal JavaScript async APIs.

import Zone from "can-zone";
import fs from "fs";

fs.readFile( "data.json", "utf8", Zone.waitFor( function() {

    // We waited on this!
} ) );