Stupidity, outrage, vanity, cruelty, iniquity, bad faith, falsehood - we fail to see the whole array when it is facing in the same direction as we - Jean Rostand

• Better Node with ES6, Pt. I
• Better JavaScript with ES6, Pt. II: A Deep Dive into Classes
• JavaScript Transpilers: What They Are & Why We Need Them

The every method executes the provided callback function once for each element present in the array until it finds one where callback returns a falsy value. If such an element is found, the every method immediately returns false. Otherwise, if callback returns a truthy value for all elements, every returns true. callback is invoked only for indexes of the array which have assigned values; it is not invoked for indexes which have been deleted or which have never been assigned values.This method returns true for any condition put on an empty array. -MDN

some() executes the callback function once for each element present in the array until it finds one where callback returns a truthy value (a value that becomes true when converted to a Boolean). If such an element is found, some() immediately returns true. Otherwise, some() returns false. callback is invoked only for indexes of the array which have assigned values; it is not invoked for indexes which have been deleted or which have never been assigned values.This method returns false for any condition put on an empty array. - MDN

Scenario One

const add = (...entries) => {
  return entries
    .filter(Number.isInteger)
    .reduce((sum, int) => {
      return sum + int;
    }, 0);
};

const add = (...entries) => {
  return entries.reduce((sum, entry) => {
    if(Number.isInteger(entry)) {
      return sum + entry;
    }
    return sum;
  }, 0);
};

Enter .some()

const add = (...entries) => {
  let theSum = 0;
  if(hasTwoOrMoreInts(entries)){
    // there are >= 2 integers, lets sum them
    theSum = entries.reduce((sum, entry) => {
      if(Number.isInteger(entry)) {
        return sum + entry;
      }
      return sum;
    }, 0);
  }
  return theSum;
};

const hasTwoOrMoreInts = (entries) => {
  let lastIndex = -1;
  let hasMinimumIntsCount = false;

  const hasAnInt = entries.some((entry, index) => {
    lastIndex = index;
    return Number.isInteger(entry);
  });

  if(hasAnInt === true) {
    // we've got one int, is there another?
    const hasMoreInts = entries.slice(lastIndex + 1).some(Number.isInteger);
    hasMinimumIntsCount = (hasMoreInts === true) && hasAnInt;
  }

  return hasMinimumIntsCount;
};

Scenario Two

const add = (...entries) => {
  let theSum = 0;
  const nonInts = entries.filter(entry => !Number.isInteger(entry));
  if(nonInts.length === 0) {  // are there non-ints?
    theSum = entries.reduce((sum, int) => {
      return sum + int;
    }, 0);
  }
  return theSum;
}

Enter .every()

const add = (...entries) => {
  let theSum = 0;
  const areAllInts = entries.every(Number.isInteger);
  if(areAllInts === true) {  // are these indeed all ints?
    theSum = entries.reduce((sum, int) => {
      return sum + int;
    }, 0);
  }
  return theSum;
};

const requiredFields = Array.of(
  isFirstNameValid(),
  isLastNameValid(),
  isEmailValid(),
  isAboutMeValid()
);

const optionalFields = Array.of(
  isTwitterValueValid(),
  isFacebookValue(),
  isGoogleplusValueValue()
);

const isValid = (inputStatus) => inputStatus === true;

if(requiredFields.every(isValid) && optionalFields.some(isValid)) {
  // all required fields are valid
  // and at least one social media field is valid
  // lets proceed to submit the form now :D
} else {
    // lets tell the user we are serious here!
    // this will happen really fast since we are short-circuting 
    // with .some and .every above
}

1. A .filter() immediately followed by .forEach(), or .map(), or .reduce() or any chained combination involving them
2. A .filter() immediately followed by a condition examining the result of the invocation, and where the body of the condition contains a .forEach() , or .map(), or .reduce() or any chained combination involving them, acting on the result from the .filter()