Truthy and Falsy

Deepankar Bhade / June 12 , 2021
1 min read--

Each value in javascript has a Boolean value associated with it we can try to understand it with this example.

index.js
let x; if(x){ console.log('True runs') }else{ console.log('False runs') } // OUTPUT: // "False runs"

The false statement runs but why does this happen? This is where truthy & falsy come into action.

All values in javascript when used in a Boolean context inherit a boolean value. In the above example, the variable x was undefined and is considered false when encountered in a Boolean context hence falsy.

Values that are considered falsy in javascript

  • false
  • 0 , -0
  • 0n
  • "" , '' (empty string)
  • null
  • undefined
  • NaN
  • document.all

Every value that is not falsy is truthy:

index.js
let x = 10; if(x){ console.log('True runs') }else{ console.log('False runs') } // OUTPUT: // "True runs"

Here x does not come under any falsy value therefore is truthy.


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