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JavaScript Empty Array


/* ToNumber(ToPrimitive([])) == ToNumber(false) */
[] == false; // true

When [].toString() is executed it calls [].join() if it exists, or Object.prototype.toString() otherwise. This comparison is returning true because [].join() returns '' which, coerced into 0, is equal to false ToNumber.

Beware though, all objects are truthy and Array is an instance of Object:

// Internally this is evaluated as ToBoolean([]) === true ? 'truthy' : 'falsy'
[] ? 'truthy' : 'falsy'; // 'truthy'