JavaScript is full of inconsistent APIs. Wrapping those APIs in functions allows you to have full control over how to configure them and make them more reusable.

This becomes even more beneficial when dealing with the async nature of JavaScript. You'll learn how a broadcaster is a function that wraps another function (which we call listeners) and modifies the behavior. We will build up this pattern in a way that allows you to compose broadcasters together making your code more reusable.

**You're in Section 02 of [Composing Closures and Callbacks in JavaScript](https://egghead.io/playlists/composing-closures-and-callbacks-in-javascript-1223)**

JavaScript is full of inconsistent APIs. Wrapping those APIs in functions allows you to have full control over how to configure them and make them more reusable. This lesson walks through wrapping setTimeout in a function that allows you to pass in custom times and callbacks independently.

Create a Function to Configure setTimeout

Cancelation is huge part of async code, but again, APIs in JavaScript are inconsistent. We can develop our own pattern to allow us full control over how cancelation behaves so that our functions can work together.

Return a Function to Cancel an Async Behavior

As we develop our pattern further, we can see how it can apply to all async scenarios in JavaScript. All user events go through addEventListener, so making sure we have control over how addEventListener interacts with other APIs, like setTimeout, gives us confidence in our pattern moving forward.

Wrap addEventListener in a Function for More Control

We also need to control setInterval since so many async scenarios rely on timers. The pattern we've created so far matches up nicely and our confidence grows that we'll be able to use these functions together.

Create a Utility Function to Control setInterval

We've reached the point where established broadcasters and we can begin to use them together. This lesson walks through creating a `merge` function which can take two broadcasters and listen to both of them.

Combine Multiple Async Behaviors with a Merge Function

Functions returning functions returning functions can begin to look a bit unwieldy. The arrow function has helped the syntax a lot, but maybe using a `curry` utility function to combine all the arguments into a single function will help your syntax look a little cleaner. Currying isn't necessary for our pattern, but you'll definitely see it used in many patterns involving functions returning functions and maybe you'll grow to love it.

Use Lodash Curry When Functions Return Functions

Functions returning functions returning functions can begin to look a bit unwieldy. The arrow function has helped the syntax a lot, but maybe using a curry utility function to combine all the arguments into a single function will help your syntax look a little cleaner. Currying isn't necessary for our pattern, but you'll definitely see it used in many patterns involving functions returning functions and maybe you'll grow to love it.

Match Function Requirements with Lodash Partial and Flip

Create a Buffer to Pair Values Together with Zip

The patterns we've established can also work well with plain old Objects and Arrays. We just have to capture the behavior of accessing those values inside of our broadcaster so the values can be passed down into a listener.

Pass an Array to a Callback with a forOf Function

All good things come to an end. The concept of "done" plays a large part in our pattern and asynchronous code in general. We have to be able to handle when a broadcaster has completed its passing values so we can know what to do next.

## Congrats on finishing Section 02: Establish Callback and Closure patterns Around Async Browser Behaviors!🎉🎉

  👉  **[CLICK HERE to continue to the next section, Use the Callback and Closure Pattern to Build Advanced Async Behaviors.](https://egghead.io/playlists/use-the-callback-and-closure-pattern-to-build-advanced-async-behaviors-db15)** 👈 

Establish Callback and Closure patterns Around Async Browser Behaviors

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