ES6 Destructuring assignments with Objects & Arrays

get_date_range.js

// { days } creates the variable days from the default object {days: 7}
function get_date_range({ days } = {days: 7}) {
    let end = Date.now();
    let period = days * 24 * 60 * 60 * 1000;
    let start = end - period;
    let start_date = new Date(start).toISOString(); // returns the date in ISO8601 format in UTC 0
    let end_date = new Date(end).toISOString();

    console.log(start_date, '-', end_date);
    return [start_date, end_date];
}

// overrides the default value of days
get_date_range({days: 4}); // 2015-09-14T09:12:10.508Z - 2015-09-15T09:12:10.508Z

// [ start, end ] creates the variables start & end from array returned from get_date_range()
let [ start, end ] = get_date_range(); // uses the default value of 7 days

console.log(start); // 2015-09-08T09:15:10.634Z
console.log(end); // 2015-09-15T09:15:22.893Z