JavaScript - Primitive Data Types

Introduction

Namaste, In this blog post I will discuss the following topics

1. Primitive data types in JavaScript

2. Equality behaviour

3. Complete source code

Primitive Data Types In JavaScript

A primitive data type is a fundamental type that is used to hold the data in the purest form, so that

• A conversion is not required when used in the computation

• To maintain data integrity

There are 7 primitive types in JS

• undefined: When a variable is declared but is not initialized. A variable can also be initialized to undefined.

let mydata;
console.log("type: ", typeof mydata, " value: ", mydata);
// result - type: undefined value: undefined
let mydata2=2;
mydata2=undefined; // valid initialization
console.log("type: ", typeof mydata2, " value: ", mydata2);
// result - type: undefined value: undefined

• number: Can hold integer and float values.

    let mydata=30;
    console.log("type:", typeof mydata, " value:", mydata);
    // result - type: number value: 30
    mydata = 56.78;
    console.log("type:", typeof mydata, " value:", mydata);
    // result - type: number value: 56.78
  

• boolean: It is used for holding 2 states i.e. true or false.

    let mydata=false;
    console.log("type:", typeof mydata, " value:", mydata);
    // result - type: boolean value: false
    mydata = true;
    console.log("type:", typeof mydata, " value:", mydata);
    // result - type: boolean value: true
  

• bigint: It is used for holding large integers. The value is suffixed using 'n'.

    let mydata=1000000000000000000000000000000000000000000000000000000000000000000000000000000000n;
    console.log("type:", typeof mydata, " value:", mydata);
    // mydata=100.89899n; // error
  

• null: It is used for holding a 'null' value i.e. value that is not applicable. The data type for null is identified as an object (bug in Javascript)

    let mydata=null;
    console.log("type:", typeof mydata, " value:",mydata);
    // result - type : object value: null
  

• string: It is used to hold a sequence of characters.

    let mydata="Namaste Javascript";
    console.log("type:", typeof mydata, " value:", mydata);
    // result - type: string  value: Namaste Javascript
    mydata= "100";
    console.log("type:", typeof mydata, " value:", mydata);
    // result -  type: string  value: 100
  

• symbol: It is used to hold unique values. The values are immutable. Symbols can be used as property keys in an object.

    let sym = Symbol("EmpNo");
    let sym2 = Symbol("EmpName");
  
    console.log("Compare", sym === sym2);
    //Result - Compare false
  
    let employee = {
        [sym] : 100,
        [sym2] : "Ram"
    };
  
    console.log("object", employee);
    //Result - object {Symbol(EmpNo): 100, Symbol(EmpName): 'Ram'}
  

Equality Behaviour

The primitive types are compared by value, not by reference.

let mydata= 100;
let mydata2 = 200;


console.log("comapare-number", mydata === mydata2);
//result - comapare-number false

mydata="ram";
mydata2="ram";
console.log("compare string", mydata === mydata);
//result - compare string true

mydata=false;
mydata2=false;
console.log("compare boolean", mydata === mydata);
//result - compare boolean true

Complete Source Code

Program 1

//Objective - Program to demonstrate primitive data types in JavaScript
//Author - Mahavir DS Rathore

let mydata;
console.log("type: ", typeof mydata, " value: ", mydata);
// result - type: undefined value: undefined

mydata=30;
console.log("type:", typeof mydata, " value:", mydata);
// result - type: number value: 30

mydata = 56.78;
console.log("type:", typeof mydata, " value:", mydata);
// result - type: number value: 56.78

mydata=false;
console.log("type:", typeof mydata, " value:", mydata);
// result - type: boolean value: false

mydata = true;
console.log("type:", typeof mydata, " value:", mydata);
// result - type: boolean value: true

mydata=1000000000000000000000000000000000000000000000000000000000000000000000000000000000n;
console.log("type:", typeof mydata, " value:", mydata);
// mydata=100.89899n; // error

mydata=null;
console.log("type:", typeof mydata, " value:",mydata);
// result - type : object value: null 

mydata="Namaste Javascript";
console.log("type:", typeof mydata, " value:", mydata);
// result - type: string  value: Namaste Javascript

mydata= "100";
console.log("type:", typeof mydata, " value:", mydata);
// result -  type: string  value: 100

let sym = Symbol("EmpNo");
let sym2 = Symbol("EmpName");

console.log("Compare", sym === sym2);
//Result - Compare false

let employee = {
    [sym] : 100,
    [sym2] : "Ram"
};

console.log("object", employee);
//Result - object {Symbol(EmpNo): 100, Symbol(EmpName): 'Ram'}