To read more about it check out the MDn docs for Array.prototype.

This article is inspired by Jake Dohm's video which I encourage you to check out.

map().įeel free to play around with the codepen I created. And of course we could in fact add more than one item to the names array if we wanted to. entries Each item in this loop is an Array with first the key and then the element. Via the iterator protocol, we can loop over data types that don’t default support for that. An object doesn’t have built-in functionality to loop over it. We can add more keys to the objects in our people array and we will receive these new keys without having to modify anything thanks to the use of the spread operator. In JavaScript, some types of data (Array or Map) have built-in functionality to loop over. A key in the Map may only occur once it is unique in the Maps collection.A Map object is iterated by key-value pairs a for.of loop returns a 2-member array of key, value for each iteration. We now have a new array of names with a fullName plus the first and last names. Map objects are collections of key-value pairs. const people = const people = [ )Īnd that's it. duplicate>JavaScript associative array object, That function returns the own keys of an object, as an array: Object.keys(arrjqTabContents. Inside these smaller boxes we can have a string of text or numbers or Objects. So the box in position 0 will be the first box and box with position 1 will be the second box. Think of it like a a big box that inside it has some smaller boxes which can be found by their index. An array is a data structure that contains a group of elements. map() method let's just recap on what is an array. a simple old-fashioned for loop - async-friendlyįor (let index = 0 index

forEach (ES5+ only spec | MDN) (or its relatives some and such) - not async-friendly (but see details).

a for-of loop (ES2015+ only spec | MDN) - simple and async-friendly.

For each javascript array of objects