How to convert a String to a Boolean in JavaScript

There are three most accessible and common ways to convert a string to a boolean in JavaScript, which are using the Boolean() function, using the logical NOT (!) operator, and using the identity operator (===). Let’s follow this article to learn more about how to use the three methods above.

Convert a String to a Boolean in JavaScript

Using Boolean() function

JavaScript provides the Boolean() function that permits users to convert other types to a boolean type. We can exploit this function to convert a string to a boolean. 

In this way, non-empty objects are evaluated as “true” even if the string value is “false”.

For instance:

let myString1="LearnShareIt";
console.log(Boolean(myString1));

let myString2="false";
console.log(Boolean(myString2));

Output:

True
True

Empty objects like: "", 0, undefined, null, NaN, and false are evaluated as “false”.

For instance:

console.log(Boolean(false)); // False 		
console.log(Boolean(0)); // False 			
console.log(Boolean(NaN)); // False 	 		
console.log(Boolean("")); // False	 		
console.log(Boolean(null)); // False			
console.log(Boolean(undefined)); // False	

Output:

False
False
False
False
False
False

Using Logical NOT (!) operator

The ! compel value we need to convert to a boolean, but it will reverse the result, so if we want to invert the result back, we have to put another !. The !! operator returns the same result as the Boolean() function.

Try using the ! operator 

For instance:

let myString1 = "";
console.log(!myString1); 

let myString2 = "LearnShareIt";
console.log(!myString2);

Output:

True
False

Because of the reverse result caused by the ! operator leads to 2 opposite consequences:

myString1 is “” with the result will be “false” but now we receive “true”

myString2 is “LearnShareIt” as a result will be “true” but the ! operator converts the outcome into “false“

Now try using the !! operator

For instance:

let myString1 = "";
console.log(!!myString1); 

let myString2 = "LearnShareIt";
console.log(!!myString2);

Output:

False
True

An !! operator will reverse the result of the ! operator 

Using Identity Operator (===)

The identity operator is known as a strict operator. This operator will validate the value and the type of the operands. It only compares two values and returns true if they are compared and have the same value and type. We can use the identity operator to convert a string to a boolean by comparing the string that needs to be converted with “true”. This way will return a boolean true if the string is actually “true” and return a boolean false with others.

For instance:

// Try with the string "true".
let myString1 = "true"; 
let boolValue1= (myString1 === "true");
console.log(boolValue1);

// Try with other string 
let myString2 = "false"; 
let boolValue2= (myString2 === "true");
console.log(boolValue2);"

Output:

True 
False

Summary

In this article, I have introduced three common ways to convert a string to a boolean in JavaScript. Each method has its strengths and weaknesses, and you can select the most approachable way. But I encourage you to use the identity operator. This method will return a boolean true as long as the string is “true” and a boolean false with other strings. Although ways using the Boolean() function or logical NOT (!) operator are both accessible and convenient, these approaches will return a boolean true if the string is not empty even if the string value is “false”. You may want a different result.

Mary Ralston

Hi, I’m Mary Ralston. I have experience programming in HTML, javascript, C++,… and I want to share with you my experience. So if you want to know more about the above languages read my articles