Reflections: Javascript Objects
On Friday I read YDKJS — this and Object protoypes for an hour, then worked on my blog for an hour.
Reflections on Chapter 3: Objects.
First, not everything in Javascript is an object. There are six primary types in JS, which are strings, numbers, booleans, null, undefined, and objects.
Objects can have “sub-types,” such as functions or arrays. These are called complex primitives. This terminology is particularly confusing, because you would think they are a type of primitive, but they’re actually a type of object.
There are also other object sub-types, called “Built-in” objects. These are actually functions that can be used as constructors, or a function called with the new operator. They make objects. Check out the code below:
var strPrimitive = “I am a string”;typeof strPrimitive ; // stringstrPrimitive instanceof String; // falsevar strObject = new String(“I am a string”);typeof strObject = strObject; // objectstrObject instanceof String // true
You can see here that strPrimitive is a primitive string, while strObject is an object.
In the case of String objects, there is apparently little use for them except for the fact that you can store properties on them.
It’s possible to iterate over the values (rather than properties or indices) in Javascript objects and arrays with the ES6 for… of syntax. Arrays have this function built-in, while a custom made one must be made for objects.
