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.
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();
// → 5Here, we have array and object. The first chain uses the size() function to count the number of properties after omitting the first property. The second chain wraps the array and, after dropping 5 items, counts what's left.