Comparing the .some() and .every() functions in JavaScript to the "At Least One" rule

01-coin-tosses.js

var coinTosses = [
  { isHeads: true,  user: 'Michael', time: 1485954569 },
  { isHeads: false, user: 'Michael', time: 1485954575  },
  /* ... etc ... */
];

02-condition.js

var condition = function( coinToss ) {
  return coinToss.isHeads;
}

03-every-using-for-loop.js

var allHeads = true;
for( var i = 0; i < coinTosses.length; i++ ) {
  if( ! condition( coinTosses[i] ) ) {
    allHeads = false;
  }
}

04-using-every.js

var allHeads = coinTosses.every( condition );

05-tautology-1.js

myArray.every( condition ) === ! myArray.some( ! condition )

06-tautology-2.js

myArray.some( condition ) === ! myArray.every( ! condition )