What are truthy and falsy values in JavaScript?

A value is either truthy or falsy depending on how it is evaluated in a Boolean context. Falsy means false-like and truthy means true-like. Essentially, they are values that are coerced to true or false when performing certain operations.

There are 6 falsy values in JavaScript. They are:

  • false
  • undefined
  • null
  • "" (empty string)
  • NaN
  • 0 (both +0 and -0)

Every other value is considered truthy.

A value’s truthiness can be examined by passing it into the Booleanfunction.

Boolean("") // false
Boolean([]) // true

There is a shortcut for this using the logical NOT ! operator. Using ! once will convert a value to its inverse boolean equivalent (i.e. not false is true), and ! once more will convert back, thus effectively converting the value to a boolean.

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