Collecting my solutions for a great tutorial...

01 eloquentjavascript.net

Every chapter of eloquentjavascript.net has some exercises, which i keep here for reference.

04_data.html#p_kFIc5gkwlo.js

function deepEqual(obj1, obj2){
  if ( isObject(obj1) && isObject(obj2) ) {
    if ( samePropCount(obj1, obj2) ) {
      for (var property in obj1) {
        if ( obj2.hasOwnProperty(property) ){
          return deepEqual( obj1[property], obj2[property] );
        } else {
          return false;
        }
      }
    } else {
      return false;
    }
  } else {
    return obj1 === obj2;
  }
}
 
function isObject(obj){
  return (obj == null) ? false : typeof obj == 'object';
}
 
function samePropCount(obj1, obj2){
  return Object.keys(obj1).length === Object.keys(obj2).length;
}
 
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

05_higher_order.html#p_a44KIXR4aT.js

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.
function motherAge(person) { 
  return person.born - byName[person.mother].born;
}
function hasMother(person){
  return byName[person.mother];
}
console.log( average( ancestry.filter(hasMother).map(motherAge) ) );

// → 31.2

05_higher_order.html#p_aMPYznovUm.js

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

function some(array, f){
  for( i=0; i<array.length; i++ ) {
    if ( f(array[i]) === true ) 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

05_higher_order.html#p_d8oC4azbX1.js

function transparentWrapping(f) {
  return function() {
    return f.apply(null, arguments);
  };
}
 
var funcWithArgs = transparentWrapping(function() {
  return arguments;
});
var funcWithoutArgs = function(arguments) {
  return arguments;
};
 
console.log( funcWithArgs( "all args are available inside funcWithArgs even if not declared", [1,3,5], '3', {a:33,b:{a:4,b:44}} ) );
console.log( funcWithoutArgs( "only first arg available inside funcWithoutArgs", [1,3,5], '3', {a:33,b:{a:4}} ) );

05_higher_order.html#p_ENbLeUYppS.js

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

// Your code here.

function age(p) { return p.died - p.born; }

function century(p){
  return Math.ceil(p.died / 100);
}

function gender(p){
  return p.sex;
}

function gender(p){
  return p.sex;
}

function group(array, by){
  var grouped = {};
  array.forEach(function(p) {
    var prop = by(p);
    if ( grouped.hasOwnProperty( prop ) ) {
      grouped[prop].push(p);
    } else {
      grouped[prop] = [];
      grouped[prop].push(p);
    }
  });
  return grouped;
}

function averageAge(array){
  return average( array.map(age) ); 
}

function logAverageAge(obj){
  for (var prop in obj) {
    console.log( prop + ': ' + averageAge(obj[prop]) );
  }
}

logAverageAge( group(ancestry, century) );

// Bonus!!
logAverageAge( group(ancestry, gender) );

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

05_higher_order.html#p_RqAkArolEa.js

var arrays = [[1, 2, 3], [4, 5], [6]];
// Your code here.
console.log(arrays.reduce(function(newArr, currArr) {
  return newArr.concat( currArr );
}));