Explain when() methods in Collect.js?

Collect.js - Interview Questions

when() : The when() method will execute the given callback when the first argument given to the method evaluates to true:

const collection = collect([1, 2, 3]);

collection.when(true, items => items.push(4));

collection.all();

// [1, 2, 3, 4]

whenEmpty() : The whenEmpty() method will execute the given callback when the collection is empty:

const collection = collect([]);

collection.whenEmpty(c => c.push('Mohamed Salah'));

collection.all();

// ['Mohamed Salah']
const collection = collect(['Darwin Núñez']);

collection.whenEmpty(
  c => c.push('Mohamed Salah'),
  c => c.push('Xherdan Shaqiri'),
);

collection.all();

// [
//   'Darwin Núñez',
//   'Xherdan Shaqiri',
// ];

whenNotEmpty() : The whenNotEmpty() method will execute the given callback when the collection is not empty:

const collection = collect(['Darwin Núñez']);

collection.whenNotEmpty(c => c.push('Mohamed Salah'));

collection.all();

// [
//   'Darwin Núñez',
//   'Mohamed Salah',
// ]
const collection = collect(['Darwin Núñez']);

collection.whenNotEmpty(
  c => c.push('Mohamed Salah'),
  c => c.push('Xherdan Shaqiri'),
);

collection.all();

// [
//   'Darwin Núñez',
//   'Mohamed Salah',
// ];