Data Types or Value Types in JavaScript

Data Types or Value Types in JavaScript

This article discusses about the data and data types or value and value types in JavaScript. JavaScript recognizes 5 following given values.

Values in JavaScript

  • String: “I am Ravi Bhadauria”
  • Number: 25, 25.35, -25.36
  • Boolean: true or false
  • null: It is a special keyword in JavaScript denotes to a null value
  • Undefined: A value that comes for top level and equal to undefined

Value or Data Types in JavaScript

JavaScript introduces 5 primitive data types too for the respective above given values or data.

  1. string
  2. number
  3. boolean
  4. null
  5. undefined

Data Type Conversion or Type Casting in JavaScript

All we know that JavaScript is a dynamic type language; meaning we don’t need to explicitly declare data types of the variables. It converts them automatically. JavaScript offers various functions to deal with data type conversion process. Here I will discuss few of the common ways to deal with data type conversion in JavaScript.

Converting a String to Number in JavaScript

Suppose we have a variable ‘num1′ with a value of ’55’ and another variable ‘num2’ with the value of 85. What will happen if we want total of the both variables.


var num1 = ’55’;
var num2 = 85;
alert(num1+num2); //5585

So, result would be 5585 why not 140? Because num1 value type is string. You can check using typeof() operator too. So what is the solution?

alert(Number(num1) + num2); //140

In above line we have converted the num1 variable to the number and we got the desired result.

We have some other functions to convert a string value to the number in JavaScript.

  • Number()
  • parseInt()
    alert(parseInt(num1) + num2); //140
  • parseFloat()
    alert(parseFloat(num1) + num2); //140
  • Unary + operator
    alert((+num1) + num2); //140

Number to String Conversion in JavaScript

There are various ways to do it in JavaScript. But I am explaining one of the easiest methods here.

  • String()
  • toString()
  • Quotes Mothod


var age = 45;


Or quote the value given to age variable like var age = ’45’;
Check the data type using typeof(). You will get string.

Hope this will help someone in knowing JavaScript’s data types.
Please leave your feedbacks and suggestions in comments.


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