You’re probably aware that all data is ultimately represented inside a computer as long sequences of ones and zeros—but for most day-to-day tasks, we want to think about data in a way that’s more natural to us: numbers, text, dates, and so on. We will call these abstractions data types.
A variable is essentially a named value, and as the name implies, the value can change at any time. For example, if we’re working on a climate control system, we might have a variable called
// degrees Celsius
let keyword is new in ES6; prior ...