JavaScript Data Types

Data Types refer to the types of data that can be stored in a variable. They include primitive and non-primitive data types.

The primitive data types are:

String
Number
Boolean
Undefined
Null
Symbol
The non-primitive data type is:

An object can be an array, function, date , object and Regex (Regular expression).

The major difference between the primitive and non-primitive data types is that in primitive data types, only one value can be stored while more than one value can be stored in the non-primitive type.

For the purpose of this post, we will only focus on string, number, boolean, undefined and null.

String

A group of characters surrounded by single quotes (‘’), double quotes(“”), backticks or String() method.

let str1 = 'String in single quote.';
let str2 = "String in double quote.";
let str3 = `String in backticks.`;
let str4 = String('Creating a string with String().');

Number

The number can be an integer (positive or negative), a floating point value, exponential value, Infinity or Nan (not a number).

const num1 = 1; // Positive integer
const num2 = -10; // Negative integer
const num3 = 24.3; // Floating point value
const num4 = 10e2; // Exponential value: 10*100
const num5 = 5 / 0; // Infinity
const num6 = 'hello' * 5; // Nan
let num7 = Number(10);
Num7 = Number(5);

Boolean

This is a logical data type that has two values true and false. It can be used for comparison of variables or to check a condition.

let checker = true;
const a =5, b = 9;
if (a < b) {
  // if a is less than b
  checker = true;
}
else {
  checker = false;
}
a == b; // a is equal to b returns false
a != b; // a is not equal to b returns true

Undefined

This type of data is a variable where the variable has been declared but remains undefined. A value has not been assigned.

let firstName; // Declaration
console.log(firstName); // Undefined
firstName = 'John'; // Assign the string John
console.log(firstName); // John

Null

The null data type refers to a value that means the value is absent or empty.

let x = null;
console.log(x) // null

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