A powerful use of chained function calls is building filters that successively filter out unwanted items from a larger collection. Let's say that you already have a piece of code that's using the filter() function on a collection. But now you need to alter that filtering operation, perhaps by adding additional constraints. Rather than messing around with the existing filter() code that you know works, you can build a filter chain.
The simplest approach to assembling filter chains is to join together multiple calls to the filter() function. Here's an example of what that might look like:
var collection = [
{ name: 'Ellen', age: 20, enabled: true },
{ name: 'Heidi', age: 24, enabled: false },
{ name: 'Roy', age: 21, enabled: true },
{ name: 'Garry', age: 23, enabled: false }
];
_(collection)
.filter('enabled')
.filter(function(item) {
return item.age >= 21;
})
.value();
// → [ { name: "Roy", age: 21, enabled:...