// basic merge callback
var merge = function(array1, array2, callback){  
	// error check array lengths with ternary operator
  //(array1.length != array2.length) ? return new Error('array\'s not same length') : null;
 
 	// instantiate our result array that we will return
  var result = [];
 	
  // loop through each index of array1
  array1.forEach( function(v,i) {
 		// append the return of our callback to our results array
    result.push(callback(array1[i], array2[i]));
  });
 
  return result;
}

// how you would write merge if you wanted to use the map method
var mergemap = function(array1, array2, callback) {
  return array1.map(function(v, i) {
    return v + array2[i];
  });
}

// our function call with anonymous callback
var x = merge([1, 2, 3, 4], [5, 6, 7, 8], function(a, b){  
  return a + b;
});

console.log('Merge result: ', x);
//x should now equal [6, 8, 10, 12].

// Think distance formula from physics except
// it should be able to find distance in any dimensional system
// 2D = x,y coord, 3D = x,y,z coord, etc.
var euclid = function(coords1, coords2){  
  //Your code here.
  //You should not use any loops and should
  //instead use your original merge function.
  
  // This does the (x1 - x2 - xN)^2, (y1 + y2 + yN)^2 + ...
  var dimensions = merge(coords1, coords2, function(a, b) {
    return Math.pow((a - b), 2);
  });
  
  // This sums the dimension and takes the square root
  // sqrt( x + y + z + ...)
  // .reduce is acting as a sum function for our dimension array
  // We then use Math.sqrt to get the square root
  // We use Math.round with * 100 and / 100 to round to two decimal places
  // The rounding is optional but makes for a nicer looking result
  var distance = Math.round( Math.sqrt( dimensions.reduce(function(previousVal, currentVal) {
  	return previousVal + currentVal;
	})) * 100) / 100;

	return distance;
}

var x = euclid([1.2, 3.67], [2.0, 4.4]);
console.log('Euclid result: ', x);
//x should now equal approximately 1.08.