What are the Falsey Values in JavaScript?

Falsey Values in JavaScript

In JavaScript, "falsey" values are those that evaluate to false in expressions such as if(value), value ? and !value.

List of Falsey Values

• false
• Zero of Number type: 0, -0, 0.0, 0x0
• Zero of BigInt type: 0n, 0x0n
• Strings of length 0: "", '', ``
• null
• undefined
• NaN
• document.all (in HTML browsers only)

What is "Falsey"?

"Falsey" simply means that JavaScript's ToBoolean function returns false for that value. ToBoolean underlies expressions like !value, value ? ... : ..., and if (value).

According to the official ECMAScript specification, the following rules apply to ToBoolean:

Argument type	Result
Undefined	Return false
Null	Return false
Boolean	Return argument
Number	If argument is 0, -0, or NaN, return false; otherwise, return true
String	If argument is an empty string (length 0), return false; otherwise, return true
BigInt	If argument is 0n, return false; otherwise, return true
Symbol	Return true
Object	Return true

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