Truthy and Falsy

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

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:

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.