The Boolean data type in JavaScript can store one of two possible values: true or false. Boolean values are the result when you do comparisons in JavaScript. If you ask JavaScript something like: "Is 3 equal to 30?," it will respond with a Boolean value of false.
The Boolean data type is named after the mathematician George Boole, so it's always capitalized.
Do a few experiments with Booleans. Open the JavaScript Console and try typing each of the following statements, pressing Return or Enter after each one to see the result. Note that a single‐line comment is used after each statement to explain what it means. You don't need to type these comments into the console, but you can if you want.
1 < 10 // Is 1 less than 10? 100 > 2000 // Is 100 greater than 2000? 2 === 2 // Is 2 exactly equal to 2? false === false // Is false exactly equal to false? 40 >= 40 // Is 40 greater than or equal to 40? Boolean (0) // What is the Boolean value of 0? Boolean (false) // What is the Boolean value of false? "apples" === "oranges" // Is "apples" exactly equal to "oranges"? "apples" === "apples" // Is "apples" exactly equal to "apples"?
In addition to the statements you would expect to be false, JavaScript also considers the following values to be false:
| 0 | null | undefined |
| " (an empty string) | false |