Page 188 - JavaScript

Chapter 21: Comparison Operations

Remarks

When using boolean coercion, the following values are considered "falsy":

• false
• 0
• "" (empty string)
• null
• undefined
• NaN (not a number, e.g. 0/0)
• document.all¹ (browser context)

Everything else is considered "truthy".

¹ willful violation of the ECMAScript specification

Examples

Logic Operators with Booleans

var x = true,
y = false;

AND

This operator will return true if both of the expressions evaluate to true. This boolean operator will
employ short-circuiting and will not evaluate y if x evaluates to false.

x && y;

This will return false, because y is false.

OR

This operator will return true if one of the two expressions evaluate to true. This boolean operator
will employ short-circuiting and y will not be evaluated if x evaluates to true.

x || y;

This will return true, because x is true.

NOT

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