How To Check If Type Is Boolean Using JavaScript

How to check if type is Boolean using JavaScript

Typeof operator is one of the methods to check if type is Boolean using JavaScript. In this article we will present the specific steps for you to do it. Let’s check it out!

How to check if type is Boolean using JavaScript

There are many ways to check if type is Boolean using JavaScript. It Includes built-in methods as well as comparison conditional operations. Please refer to the two ways below.

Typeof operator

Usually, in JavaScript, the typeof operator will return a string that represents the type of operand’s value.

Syntax:

typeof input

Parameters:

  • input: The variable needs to check the data type.

It not only returns Boolean data type results but can also check data types of all other data types in Javascript. So in my opinion it is a perfect tool and should be used often.

If we want to manually check if the data type is Boolean, you can do like this:

let check = true
console.log(typeof check)

Output

Boolean

Or 

let check = true
console.log(typeof check === "boolean")

Output

true

However, this approach will not work if you replace typeof with instanceof.

let check = true
console.log(true instanceof Boolean)

Output

false

The instanceof operator checks whether an object is an instance of a specific class or an interface.

If the object is not properly initialized with a constructor, it returns false.

let check = new Boolean(true)

//show the result
console.log(check instanceof Boolean)

Output

true

In addition, we can create a function that only checks for Boolean data types. Follow that method right here.

Function to check the data type

We will build a method to check if our input variable is a type of boolean as follow:

function isBoolean(input) {
  return input === false || input === true;
}

//show the result
console.log(isBoolean(false) )

Or

function isBoolean (...input){
  return !! input === true || !!input  == false
}

//show the result
console.log(isBoolean(false) )

I create a function that takes input as an argument. This argument is a variable that can take any variable of any data type. Inside the function, handle an effortless statement. If the parameter is true or false (It is compared with two true and false variables combined with the |) it will return true. If it is outside these two values, it will return false. The operator === comparison means comparing data types with each other.

The function above can also be written with an arrow function.

isBoolean = (input ) => typeof input === "boolean"

Output 

True

Summary

This tutorial shows you how to check if type is Boolean using JavaScript. Each approach is helpful in each case, but each method has its limitations, so be careful when using it. Let’s try this method to get your desired results! Thanks for reading!

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