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Types in JavaScript

Explore the different types in JavaScript, focusing on primitive types like booleans, numbers, strings, symbols, null, and undefined, and their characteristics. Understand the immutability of primitives and the uniqueness of symbols, along with an introduction to objects and functions as non-primitive types.

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Types of types

Types in JavaScript group together similar kinds of values. We can further categorize these types into the following:

  • Primitive values
  • Objects and functions

Let’s look at these in detail.

Primitive values

Primitive values are immutable values in JavaScript.

Before we see an example, let’s forget what immutable means outside of a coding context. Below is a visualization of how an increment operator works.

The above visualization outlines how primitives are immutables. The important takeaway is that a primitive itself cannot be modified, but new primitives can be created, and those values are assigned to variables.

Following are all types that fall under the primitive category:

  • Boolean
  • Number
  • Null
  • Undefined
  • String
  • Symbol

Let’s explore them individually.

Boolean

These are values that take only the values true and false.

Node.js
var bool_true = true; // initialize variable to true
var bool_false = new Boolean(false); // initialize variable to false
// print values
console.log('The values are:',bool_true,bool_false);
// print types
console.log('The types are:',typeof(bool_true),typeof(bool_false));

In the above code, we can see the two ways of initializing boolean variables on line 1 and 2. Printing their values and types in the following line confirms our initialization.

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