Lo-Dash Essentials

Counting items

A variation on the previous topic—Testing truth conditions—is counting items in a collection after their values have moved through a processing chain. For example, we might need to know how many items in a collection meet the given criteria. We can get that number using a call chain.

Using length and size()

The size() function is handy because we can call it directly on a Lo-Dash wrapper. This is the preferred way to count the resulting items in our collection after our chain runs:

var object = { first: 'Charlotte', last: 'Hall' },
    array = _.range(10);

_(object)
    .omit('first')
    .size();
// → 1

_(array)
    .drop(5)
    .size();
// → 5

Here, we have array and object. The first chain uses the size() function to count the number of properties after ...