Chapter 12. Boolean()

Conceptual Overview of Using the Boolean() Object

The Boolean() constructor function can be used to create boolean objects, as well as boolean primitive values, that represent either a true or a false value.

In the code below, I detail the creation of boolean values in JavaScript.

Live Code

<!DOCTYPE html><html lang="en"><body><script>

// create boolean object using the new keyword and the Boolean() constructor
var myBoolean1 = new Boolean(false); // using new keyword
console.log(typeof myBoolean1); // logs 'object'

/* create boolean literal/primitive by directly using the number constructor 
without new */
var myBoolean2 = Boolean(0); // without new keyword
console.log(typeof myBoolean2); // logs 'boolean'

// create boolean literal/primitive (constructor leveraged behind the scene)
var myBoolean3 = false;
console.log(typeof myBoolean3); // logs 'boolean'
console.log(myBoolean1, myBoolean2, myBoolean3); // logs false false false

</script></body></html>

Boolean() Parameters

The Boolean() constructor function takes one parameter to be converted to a boolean value (i.e., true or false). Any valid JavaScript value that is not 0, −0, null, false, NaN, undefined, or an empty string(""), will be converted to true. Below, we create two boolean object values. One true, one false.

Live Code

<!DOCTYPE html><html lang="en"><body><script>

// parameter passed to Boolean() = 0 = false, thus foo = false
var foo = new Boolean(0)
console.log(foo);

// parameter passed to Boolean() ...

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