December 2012
Beginner
164 pages
3h 15m
English
Content preview from JavaScript EnlightenmentBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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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.
<!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.
<!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() = Math ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.