Simplifying JavaScript

Tip 14

Iterate Over Key-Value Data with Map and the Spread Operator

In this tip, you’ll learn how to iterate directly over key-value data in maps with either loops or the spread operator.

In the previous tip, you saw how maps are an improved key-value collection when you’re regularly adding or deleting items. As you saw, objects are very useful, but there are times when a map has distinct advantages. You can see those advantages on the Mozilla Developer Network.^[16]

You’ve already explored several advantages pertaining to when keys are set. Now you’re going to explore another suggested usage for maps: collections that are iterated.

Objects are very frustrating to iterate over. In fact, there used to be no way to directly iterate over them. You ...