How JavaScript Is Defined: From ECMAScript to Array.prototype.map

We use JavaScript every day through syntax such as: const numbers = [1, 2, 3]; const doubled = numbers.map(number => number * 2); We know what map() does, but there is a more interesting question underneath: Who decided that map() should behave this way? Why does it skip empty array slots? Why does its callback receive the value, index, and array? Why can Array.prototype.map even be used with objects that are not arrays? The answers are not specific to Chrome, Firefox, or Node.js.