[Javascript] Data Types and Object

A data type is a classification of data which tells the compiler or interpreter how the programmer intends to use the data.

A value in JavaScript is always of a certain type. For example, a string or a number.

There are 8 basic data types in JavaScript.

Seven primitive data types:

• number for numbers of any kind: integer or floating-point, integers are limited by ±(253-1).
• bigint for integer numbers of arbitrary length.
• string for strings. A string may have zero or more characters, there’s no separate single-character type.
• boolean for true/false.
• null for unknown values – a standalone type that has a single value null.
• undefined for unassigned values – a standalone type that has a single value undefined.
• symbol for unique identifiers. (new to ES6)

And one non-primitive data type:

• object for more complex data structures.

We will go throught all of them in this article. Let’s step!

Table of contents

What is typeof operator?

JavaScript provides a typeof operator that can examine a value and tell you what type it is.

• Usually used as typeof x, but typeof(x) is also possible.
• Returns a string with the name of the type, like “string”.
• For null returns “object” – this is an error in the language, it’s not actually an object

let transform;
typeof transform; // "undefined"

transform = "hello there";
typeof transform; // "string"

transform = 22;
typeof transform; // "number"

transform = false;
typeof transform; // "boolean"

transform = undefined;
typeof transform; // "undefined"

transform = null;
typeof transform; // "object" -- so confusing

transform = { clothes: "red" };
typeof transform; // "object"

transform = ["clothes", "hair", "materials"];
typeof transform; // "object"

transform = Symbol("Any thing here");
typeof transform; // "symbol"

What is the object type?

The object type refers to a compound value where you can set properties (named locations) that each hold their own values of any type.