A JavaScript Booleans represents one of two values they are as follows: 

• True 
• False

Boolean Values Very often, in programming, you will require a data type that can only have one of two values, like

• YES / NO
• ON / OFF
• TRUE / FALSE

For the above, JavaScript has a Boolean data type. It can only take the values true or false.

The Boolean() Function to find out if a variable or an expression is true, Everything Without a "Value" is False, The Boolean value of 0 (zero) is false:

var x = 0;
Boolean(x); // returns false