Truthy vs Falsy

A falsy (or falsey) value is a value that is considered false in a Boolean context. All other values are considered truthy: true in a boolean context.

JavaScript will coerce the value to a Boolean if the context requires it, such as in conditionals and loops.

8 Falsy values

Examples

if ({}) {
  console.log("Hi!");
} else if ("false") {
  console.log("Hola!");
} else if (-1) {
  console.log("Bonjour!");
} else {
  console.log("Bye!");
}

// prints "Hi!"

if (!"false") {
  console.log("Hi!");
} else if (!-Infinity) {
  console.log("Hola!");
} else if (![]) {
  console.log("Bonjour!");
} else {
  console.log("Bye!");
}

// prints "Bye!"