Skip to Content
Learning JavaScript Data Structures and Algorithms - Third Edition
book

Learning JavaScript Data Structures and Algorithms - Third Edition

by Loiane Avancini
April 2018
Beginner to intermediate content levelBeginner to intermediate
426 pages
10h 19m
English
Packt Publishing
Content preview from Learning JavaScript Data Structures and Algorithms - Third Edition

Truthy and falsy

In JavaScript, true and false are a little bit tricky. In most languages, the boolean values true and false represent the true/false results. In JavaScript, a string such as Packt evaluates to true.

The following table can help us better understand how true and false work in JavaScript:

Value Type

Result

undefined

false

null

false

Boolean

true is true and false is false

Number

The result is false for +0, -0, or NaN; otherwise, the result is true

String

The result is false if the string is empty (length is 0); otherwise, the result is

true (length >= 1)

Object

true

Let's consider some examples and verify their output:

function testTruthy(val) { return val ? console.log('truthy') ...
Become 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,
and much more.
Start your free trial

You might also like

Learning JavaScript Data Structures and Algorithms

Learning JavaScript Data Structures and Algorithms

Loiane Avancini

Publisher Resources

ISBN: 9781788623872Supplemental Content