It's really nice for when you have to do operations where you want a "tuple" in Javascript. Consider the case of finding all companies along with their hires f

It's really nice for when you have to do operations where you want a "tuple" in Javascript. Consider the case of finding all companies along with their hires from the last week, but only if the company has a hire from the last week: companies.map(c => [c, employeeStorage.getEmployees(c)]) .map(([company, employees]) => [company, employees.filter(e => e.hireDate > aWeekAgo)]) .filter(([company, employees]) => employees.length > 0)