function isAlt(str) {

	let vowels = 'aeiou'
	let arr = str.split('')
	let arr2 = []
	for (var i=0;i<arr.length;i++){
		 vowels.indexOf(arr[i]) !== -1 ? arr2.push(1) : arr2.push(2)
	}
 for (  i=1;i<arr.length;i++){
 	if (arr[i] == arr[i-1])   { return false }
 }
 return true
}

  isAlt("amazon") // true
  isAlt("apple") // false