Calculate the number of difference days between two dates

const diffDays = (date, otherDate) => Math.ceil(Math.abs(date - otherDate) / (1000 * 60 * 60 * 24));

// diffDays(new Date('2014-12-19'), new Date('2020-01-01')) === 1839

Getting the last element of a split string array

How to use the spread operator to flatten array of objects in javascript

jQuery on hover

Jquery on mouse over example.

Using promises to catch errors

Rest Operator for Objects

Now we can use rest on the properties of an Object. It allows us to explicitly extract certain named variables, and assign any uncalled variables into a catchall Object.