Андрей

!(returnDateTime <= startDate || pickupDateTime >= endDate)

function toggleFullScreen() {
      if (!document.fullscreenElement &&    // alternative standard method
          !document.mozFullScreenElement && !document.webkitFullscreenElement) {  // current working methods
        if (document.documentElement.requestFullscreen) {
          document.documentElement.requestFullscreen();
        } else if (document.documentElement.mozRequestFullScreen) {
          document.documentElement.mozRequestFullScreen();
        } else if (document.documentElement.webkitRequestFullscreen) {
          document.documentElement.webkitRequestFullscreen(Element.ALLOW_KEYBOARD_INPUT);
        }
        return true
      } else {
        if (document.cancelFullScreen) {
          document.cancelFullScreen();
        } else if (document.mozCancelFullScreen) {
          document.mozCancelFullScreen();
        } else if (document.webkitCancelFullScreen) {
          document.webkitCancelFullScreen();
        }
        return false
      }
    }

toggleFullScreen() && document.body.style.display = ('none');

function toggleFullScreen() {
      if (!document.fullscreenElement &&    // alternative standard method
          !document.mozFullScreenElement && !document.webkitFullscreenElement) {  // current working methods
        if (document.documentElement.requestFullscreen) {
          document.documentElement.requestFullscreen() && return true;
        } else if (document.documentElement.mozRequestFullScreen) {
          document.documentElement.mozRequestFullScreen() && return true;
        } else if (document.documentElement.webkitRequestFullscreen) {
          document.documentElement.webkitRequestFullscreen(Element.ALLOW_KEYBOARD_INPUT) && return true;
        }
      } else {
        if (document.cancelFullScreen) {
          document.cancelFullScreen() && return false;
        } else if (document.mozCancelFullScreen) {
          document.mozCancelFullScreen() && return false;
        } else if (document.webkitCancelFullScreen) {
          document.webkitCancelFullScreen() && return false
        }
      }
    }

toggleFullScreen() && document.body.style.display = ('none');

//var initialData = [1, 9, 4, 95, -3, 51, 6, 9, 4, 4,-9, 88, 27];
var initialData = [2, 2, 2, 2, 2, 2, 2, 2, 2, 2];

var wayFirst = function(data) { 
  var sum = 0;
  data.forEach( (value) => {sum = sum + value} )
  return sum;
}

var waySecond = function(data) {
  var sum = 0;
  data.forEach( (value, i) => {
    i % 2 === 0 ?  sum = sum + value : false
  })
  return sum;
}

var wayThird = function(data) {
  var sum = 0;
  var iTemp = 0
  data.forEach( (value, i) => { 
    if (!iTemp || iTemp + 4 === i)  { 
      sum = sum + value;
      iTemp === 0 ? iTemp = 1 : iTemp = i;
    } 
  })
  return sum;
}

console.log(wayFirst(initialData));
console.log(waySecond(initialData))
console.log(wayThird(initialData))

const initialData = [2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2]

let sumArrayWithInterval = (data, interval) => { 
  const sumWithIntervel = []; 
  let next = 0;
  data.forEach((value, i) => {
    if (next === i) { 
      const valueIndex = interval === 1 ? 1 + i : interval + 1 + i;
      
      data[valueIndex] ? sumWithIntervel.push(value + data[valueIndex]) : false
      interval === 1 ? next = i + interval + 1 : next = valueIndex + 1
    }
  })
  return sumWithIntervel;
}
console.log(
      sumArrayWithInterval(initialData, 1)
);

console.log( 
    sumArrayWithInterval(
      sumArrayWithInterval(initialData, 1)
    , 2)
);

console.log( 
  sumArrayWithInterval(
    sumArrayWithInterval(
      sumArrayWithInterval(initialData, 1)
    , 2)
  , 4)
);

var a = new F();
var b = new F();

alert(a == b);

function F() {
	if (F.instance) {
		return F.instance
	}
	F.instance = this;
}