http://eloquentjavascript.net/04_data.html Exercise solutions

EJS CH4 Exercises

// Sum of a Range
function range (start, finish, step) {
  	if (step === undefined) {
  		step = 1;
    }
	array = [];
    var reverse = false;
    step = Math.abs(step)
    console.log(start, finish, step);
    if (start > finish){
    	var temp = start;
        start = finish;
        finish = temp;
        reverse = true;
	}
  	console.log(start, finish, step);
  	for (var value=start; value <= finish; value += step){
  		array.push(value);
    }
  	if (reverse){
      	array.reverse();
  	}
  	console.log(array);
  	return array;
}

function sum (array) {
	sum = 0;
  	console.log(array);
    for (var index=0; index < array.length; index++){
    	sum += array[index];
    }
  	return sum;
}

console.log(sum(range(1, 10)));
// → 55
console.log(range(5, 2, -1));
// → [5, 4, 3, 2]



// Reversing an Array
function reverseArray(array) {
  return_array = []
  for(var index=array.length-1; index >= 0; index--){
    return_array.push(array[index]);
  }
  return return_array
}

function reverseArrayInPlace(array) {
  for(var index=0; index < (Math.ceil(array.length/2)); index++){
  	fr_v = array[index];
    bk_v = array[array.length-index-1];
    array[index] = bk_v
    array[array.length-index-1] = fr_v
  }
}

console.log(reverseArray(["A", "B", "C"]));
// → ["C", "B", "A"];
var arrayValue = [1, 2, 3, 4, 5];
reverseArrayInPlace(arrayValue);
console.log(arrayValue);
// → [5, 4, 3, 2, 1]



// A list
function arrayToList(array){
  if (array.length == 0) {
  	return null;
  }
  return {value: array.shift(), rest: arrayToList(array)}
}

function listToArray(list){
  array = [];
  for (var node = list; node; node = node.rest){
    array.push(node.value);
  }
  return array;
}

function prepend(value, list){
  array = listToArray(list);
  array.unshift(value);
  return arrayToList(array);
}

function nth(list, pos){
  array = listToArray(list);
  return array[pos];
}

console.log(arrayToList([10, 20]));
// → {value: 10, rest: {value: 20, rest: null}}
console.log(listToArray(arrayToList([10, 20, 30])));
// → [10, 20, 30]
console.log(prepend(10, prepend(20, null)));
// → {value: 10, rest: {value: 20, rest: null}}
console.log(nth(arrayToList([10, 20, 30]), 1));
// → 20



// Deep Comparison
function isObjectAndNotNull(x) {
  return (typeof(x) == "object" && x != null);
}

function deepEqual(obj1, obj2) {
  if (obj1 === obj2) {
    return true
  }
  else if (isObjectAndNotNull(obj1) && isObjectAndNotNull(obj2)) {
    if (Object.keys(obj1).length == Object.keys(obj2).length) {
      for (key in obj1) {
        if (obj2.hasOwnProperty(key)) {
          return deepEqual(obj1[key], obj2[key]);
      	}
      	else {
          return false;
        }
      }
    }
    else {
      return false;
    }
  }
  else {
    return obj1 == obj2;
  }
}

var obj = {here: {is: "an"}, object: 2};
console.log(deepEqual(obj, obj));
// → true
console.log(deepEqual(obj, {here: 1, object: 2}));
// → false
console.log(deepEqual(obj, {here: {is: "an"}, object: 2}));
// → true