The Boolean object is an object wrapper for a boolean value. Sometimes in our project, we may have a boolean value in string format (“true” or “false”), and we want its boolean equivalent (such as true or false).
JavaScript String to Boolean
To convert String to Boolean in JavaScript, use the !! operator or Boolean() function. Any string which isn’t the empty string will evaluate to true by using them.
Syntax
Boolean(value);
# OR
!!value;
Example
Let’s convert string to boolean using !! operator.
let data = "Millie Bobby Brown"
let data_bool = !!data
console.log(typeof(data_bool))
console.log(data_bool)
Output
boolean
true
You can see that !! has converted a “Millie Bobby Brown” string into a boolean value true.
How the !! works
The first ! constrain the value to a boolean and inverse it. In this case, the ! MllieBobbyBrown will return false. So to reverse it back to true, we put another ! on it. Hence the double use !!.
const data = "Millie Bobby Brown"
!data // false
!!data // true
Checkout for true or false valued strings
If you encounter a string with a value like “true” or “false”, you need to be very careful because !! will cause a problem.
const dt = "false"
console.log(!!dt)
console.log(Boolean(dt))
Output
true
true
Although it says false, it’s actually a string.
Applying !! on falsy values
In JavaScript, there are 6 falsy values. If you convert any of these to a boolean, it will return false.
console.log(!!false)
console.log(!!undefined)
console.log(!!null)
console.log(!!NaN)
console.log(!!0)
console.log(!!'')
Output
false
false
false
false
false
false
Using Boolean() method
Let’s use the boolean() method to convert.
let data = "Millie Bobby Brown"
let data_bool = Boolean(data)
console.log(typeof(data_bool))
console.log(data_bool)
Output
boolean
true
Applying Boolean on falsy values
console.log(Boolean(false))
console.log(Boolean(undefined))
console.log(Boolean(null))
console.log(Boolean(NaN))
console.log(Boolean(0))
console.log(Boolean(''))
Output
false
false
false
false
false
false
That’s it for converting JavaScript string to a boolean value.
See also
Add array to array in JavaScript

Krunal Lathiya is a Software Engineer with over eight years of experience. He has developed a strong foundation in computer science principles and a passion for problem-solving. Krunal has experience with various programming languages and technologies, including PHP, Python, and expert in JavaScript. He is comfortable working in front-end and back-end development.