JavaScript Types

JavaScript Tutorial � JavaScript Types

Data types basically specify what kind of data can be stored and manipulated within a program.

There are six basic data types in JavaScript which can be divided into three main categories:
1. primitive (or primary) as: String, Number, and Boolean
2. composite (or reference) as: Object, Array, and Function
3. special data types. Object as: Undefined and Null.

Primitive data types can hold only one value at a time, whereas composite data types can hold collections of values and more complex entities.

The String Data Type

String Data Type represent textual data. Strings are created using single or double quotes.

Example:

var x = 'Have a good day!'; // single quotes
var y = "Have a good day!"; // double quotes
var xa = "Let's have a good day"; // single quote inside double quotes
var xb = 'He said "Have a good day" and left.'; // double quotes inside single quotes
var xc = 'We\'ll have a good day.'; // escaping single quote with backslash

In JavaScript, variables can also be declared without having any initial values assigned to them. This is useful for variables which are supposed to hold values like user inputs.

Example: This example will show how JS statements look like:

// Declaring Variable
var userSurName;

// Assigning value
userSurName = "Langford";

Number Data Type - example

The number data type is used to represent positive or negative numbers with or without decimal.

Example:

<script>

var x = 74;         // integer

var y = 74.5;       // floating-point number

var z = 74.25e+7;    // exponential notation, same as 74.25e7 or 742500000

var w = 74.25e-7;    // exponential notation, same as 0.000007425



alert(12 / 0);  // Output: Infinity

alert(-12 / 0); // Output: -Infinity

alert(12 / -0); // Output: -Infinity



alert("your text" / 2);       // Output: NaN

alert("your text" / 2 + 10);  // Output: NaN

alert(Math.sqrt(-1));         // Output: NaN

  </script>

Boolean Data Type - example

The Boolean data type can hold only two values: true or false.

Used to store values like yes (true) or no (false), on (true) or off (false).

Example:

<script>

var isWorking = true;   // yes, I'm working

var iswrite = false; // no, I'm not write



var x = 4, y = 10, z = 19;


 
alert(y > x) // Output: true

alert(y > z) // Output: false

  </script>

Object Data Type

he object is a complex data type that allows you to store collections of data.

Example:

<script>

var emptyObject = {};

var person = {"name": "Salwyn", "surname": "Jara", "age": "27"};


 
// For better reading

var car = {

    "modal": "Renault Megane",

    "color": "red",

    "doors": 3

}

  </script>

Array Data Type, example

An array is a type of object used for storing multiple values in single variable.

The array index starts from 0, so that the first array element is arr[0] not arr[1].

Example: a is defined as a variable, and a is given the value 15:


<script>

var colors = ["green", "red", "yellow", "orange"];

var cities = ["Roma", "Valencia", "Madrid"];


 
alert(colors[0]);   // Output: green

alert(cities[2]);   // Output: Madrid

  </script>

javascript types of variables, of alerts, list, of functions, of arrays, errors, loops, events, objects
JavaScript Types - javascript tutorial

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