Exercises

• 3.1 A simple event: Modify the asynchronous FindRegex class so that it emits an event when the find process starts, passing the input files list as an argument. Hint: beware of Zalgo!
• 3.2 Ticker: Write a function that accepts a number and a callback as the arguments. The function will return an EventEmitter that emits an event called tick every 50 milliseconds until the number of milliseconds is passed from the invocation of the function. The function will also call the callback when the number of milliseconds has passed, providing, as the result, the total count of tick events emitted. Hint: you can use setTimeout() to schedule another setTimeout() recursively.
• 3.3 A simple modification: Modify the function created in exercise 3.2 so that it emits a tick event immediately after the function is invoked.
• 3.4 Playing with errors: Modify the function created in exercise 3.3 so that it produces an error if the timestamp at the moment of a tick (including the initial one that we added as part of exercise 3.3) is pisible by 5. Propagate the error using both the callback and the event emitter. Hint: use Date.now() to get the timestamp and the remainder (%) operator to check whether the timestamp is pisible by 5.