Posted on Mar 13, 2023

DataTypes & Conversion in JavaScript

Checking Data Types and Casting

Checking Data Types

To check the data type of a certain variable we use the typeof method.

Example:

// Different javascript data types // Let's declare different data types let firstName = "shaikhmd"; // string let lastName = "shaikh"; // string let country = "IN"; // string let city = "Mum"; // string let age = 250; // number, it is not my real age, do not worry about it let job; // undefined, because a value was not assigned console.log(typeof "shaikhmd"); // string console.log(typeof firstName); // string console.log(typeof 10); // number console.log(typeof 3.14); // number console.log(typeof true); // boolean console.log(typeof false); // boolean console.log(typeof NaN); // number console.log(typeof job); // undefined console.log(typeof undefined); // undefined console.log(typeof null); // object

Changing Data Type (Casting)

Casting: Converting one data type to another data type. We use parseInt(), parseFloat(), Number(), + sign, str() When we do arithmetic operations string numbers should be first converted to integer or float if not it returns an error.

String to Int

We can convert string number to a number. Any number inside a quote is a string number. An example of a string number: '10', '5', etc.
We can convert string to number using the following methods:

parseInt()
Number()
Plus sign(+)

let num = "10"; let numInt = parseInt(num); console.log(numInt); // 10

let num = "10"; let numInt = Number(num); console.log(numInt); // 10

let num = "10"; let numInt = +num; console.log(numInt); // 10

String to Float

We can convert string float number to a float number. Any float number inside a quote is a string float number. An example of a string float number: '9.81', '3.14', '1.44', etc.
We can convert string float to number using the following methods:

parseFloat()
Number()
Plus sign(+)

let num = "9.81"; let numFloat = parseFloat(num); console.log(numFloat); // 9.81

let num = "9.81"; let numFloat = Number(num); console.log(numFloat); // 9.81

let num = "9.81"; let numFloat = +num; console.log(numFloat); // 9.81

Float to Int

We can convert float numbers to integers.
We use the following method to convert float to int:

parseInt()

let num = 9.81; let numInt = parseInt(num); console.log(numInt); // 9

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