JavaScript difference between null, undefined and false in conditions

gistfile1.js

var isDefined = function (variable) {
  if (variable) {
    console.log( '=> ' + variable + ' defined' );
  } else {
    console.log( '=> %s \x1B[0;31mnot defined\x1B[0m', variable );
  }
}

var list = [new Date, [], {}, function(){}, 1.1, 'not-empty', true, '', NaN, false, undefined, null];

for (var i = 0; i < list.length ; i++) {
  isDefined(list[i]);
}