Mastering Immutable.js

Providing default behavior

When the caller attempts to call a behavior that doesn't exist by passing a key that doesn't exist in the behavior map, you should be able to recover from this. Thankfully, the get() method accepts a second argument that's returned if the requested key doesn't exist:

const myBehavior = action => Map.of(  true, () => console.log('thruth'),  false, () => console.log('lies')).get(  action,  () => console.log('default'))();myBehavior(true);// -> truthmyBehavior(false);// -> liesmyBehavior();// -> defaultmyBehavior(123);// -> default

The last two calls to myBehavior() result in the default behavior running because neither call is passed a key that exists. This means that the second value passed to get() is returned, which ...