EJS CH5 Exercises

// Flattening
var arrays = [[1, 2, 3], [4, 5], [6]];

//arrays = arrays.concat([5000]);
arrays = arrays.reduce(function(prev, cur) { return prev.concat(cur); });
console.log(arrays);
// → [1, 2, 3, 4, 5, 6]



// Mother-child age difference
function average(array) {
  function plus(a, b) { return a + b; }
  return array.reduce(plus) / array.length;
}


var byName = {};
ancestry.forEach(function(person) {
  byName[person.name] = person;
});


// Your code here
//console.log(average([1, 2, 3, null]))
//console.log(mothersAge(ancestry.map(function(person) {
//  if (person.mother == null) { return null; }
//  else { return person }
//}).filter(function(el){
//  return el != null;
//})));
console.log(average(ancestry.map(function(person) {
  if (byName[person.mother] == null) { return null; }
  else { return person.born - byName[person.mother].born }
}).filter(function(el){
  return el != null;
})));

// → 31.2





// Historical Life Expectancy
function average(array) {
  function plus(a, b) { return a + b; }
  return array.reduce(plus) / array.length;
}

function averageLifeByCentury(century) {
  return average(ancestry.map(function(person){
    if (Math.ceil(person.died/100) == century){
      return person.died - person.born;
    } 
    else { 
      return null; 
    }
  }).filter(function(el){
    return el != null;
  }))
}

console.log(averageLifeByCentury(16));
console.log(averageLifeByCentury(17));
console.log(averageLifeByCentury(18));
console.log(averageLifeByCentury(19));
console.log(averageLifeByCentury(20));
console.log(averageLifeByCentury(21));
// Your code here.

// → 16: 43.5
//   17: 51.2
//   18: 52.8
//   19: 54.8
//   20: 84.7
//   21: 94




// Every and then some
function forEachWithBreak(array, action){

}
function every(array, pred){
  for(var i = 0; i < array.length; i++){
    if (!pred(array[i])) {
      return false;
    }
  }
  return true;
}

function some(array, pred){
  for(var i = 0; i < array.length; i++) {
    if (pred(array[i])) {
      return true;
    }
  }
  return false;
}

console.log(every([NaN, NaN, NaN], isNaN));
// → true
console.log(every([NaN, NaN, 4], isNaN));
// → false
console.log(some([NaN, 3, 4], isNaN));
// → true
console.log(some([2, 3, 4], isNaN));
// → false