Answers for Eloquent Javascript Book

answers.js

// Answers

//  1 # Looping a triangle
//    # http://eloquentjavascript.net/02_program_structure.html#p_pP646YLlGy

var output = "";
for (var i = 1; i < 10; i++) {
    output += "#";
    console.log(output);
}

//  2 # FizzBuzz
//    # http://eloquentjavascript.net/02_program_structure.html#p_i0Cvwf75cQ

function fizzBuzz(number) {
    for (var i = 0; i <= number; i++) {
        var out = "";
        if (number % 3 === 0) {
            out += "Fizz";
        }
        if (number % 5 === 0) {
            out += "Buzz";
        }
        console.log(out || number);
    }
}

//  3 # Chess board
//    # http://eloquentjavascript.net/02_program_structure.html#p_uH3DV6RVnV

function grid(size) {
    var first = "#";
    var second = "_";
    for (var i = 0; i <= size; i++) {
        var out = "";
        for (var k = 0; k <= size; k++) {
            out += (k % 2 === 0) ? first : second;
        }
        c.log(out);
        var temp = first;
        first = second;
        second = temp;
    }
}
grid(6);

//  4 # Minimum
//    # http://eloquentjavascript.net/03_functions.html#p_aW/Uoj4mDd

function getMinimum(a, b) {
    return (a < b) ? a : b;
}

//  5 # Recursion # recursed even check
//    # http://eloquentjavascript.net/03_functions.html#p_iDq2OgBOGw

function isEven(number) {
    if (number === 0) {
        return "even";
    }
    if (number === 1) {
        return "odd";
    }
    // else { # niepotrzebne bo nie ma już gdzie pójść
    return iseven(number - 2);
    // }
}

//  6 # Bean counting
//    # http://eloquentjavascript.net/03_functions.html#p_8y74cOkS91

function countBs(string, charToFind) {
    var count = 0;
    for (var i = 0; i < string.length; i++) {
        if (string.charAt(i) === charToFind) {
            count++;
        }
    }
    return count;
}

// CHAPTER 04

//  7 # The sum of a range
//    # http://eloquentjavascript.net/04_data.html#p_fpyyiv/hm1

function range(start, end) {
    out = [];
    for (var i = start; i <= end; i++) {
        out.push(i);
    }
    return out;
}

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

function range_v2(start, end, step) {
    out = [];
    for (var i = start; i <= end; i += step || 1) {
        out.push(i);
    }
    return out;
}

function range_v3(start, end, step) {
    out = [];
    if (start < end) {
        for (var i = start; i <= end; i += step || 1) {
            out.push(i);
        }
    } else {
        for (var k = start; k >= end; k += step || -1) {
            out.push(k);
        }
    }
    return out;
}

//  8 # Reversing an array
//    # http://eloquentjavascript.net/04_data.html#p_0ysB6LgssH

function reverseArray(array) {
    var out = [];
    for (var i = 0; i < array.length; i++) {
        out[array.length - i] = array[i];
    }
    return out;
}

function reverseArray_opt1(array) {
    var out = [];
    for (var i in array) {
        out[array.length - i] = array[i];
    }
    return out;
}

function reverseArray_opt2(array) {
    var out = [];
    var lol = array.slice(0, (array.length / 2).floor);
    for (var i in lol) {
        out[lol.length - i] = array[i];
    }
    return out;
}

// 8B # Reversing an array in place

//  9 # A list
//    # http://eloquentjavascript.net/04_data.html#p_iPlgVCeZGh

// 10 # Deep comparison
//    # http://eloquentjavascript.net/04_data.html#p_xTwbRlqHNJ

// CHAPTER 5
//  1 # Flattening
//    # http://eloquentjavascript.net/05_higher_order.html#p_RqAkArolEa

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

console.log(arrays.reduce(function(a,b){ return a.concat(b) ;}));

//  2 # Mother-child age difference
//    # http://eloquentjavascript.net/05_higher_order.html#p_a44KIXR4aT

// variant 1

function hasKnownMother(person){
  return byName[person.mother] !== null ? person.mother : null;
}

console.log(average(ancestry.filter(function(){return f !== null;})));


// variant 2

function ageDifference(person){
  var mother = byName[person.mother];
  return mother ? person.born - mother.born : null;
}

console.log(average(ancestry.map(ageDifference).filter(function(f){return f !== null;})));

//  3 # Historical life expectancy
//    # http://eloquentjavascript.net/05_higher_order.html#p_ENbLeUYppS
//  3 # Every and then some
//    # http://eloquentjavascript.net/05_higher_order.html#p_BZKBxgsPML

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

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

// TEST DATA

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

jezeli podajesz funkcje w callbacku to styluj je wcieciami. inaczej ciezko to sie czyta.
nie poprawiles tez tych arrayReverse.