5) Basic Data Structures.js

// Use an Array to Store a Collection of Data
let yourArray = [1, true, "hello", false, 2];

// Access an Array's Contents Using Bracket Notation
let myArray = ["a", "b", "c", "d"];
myArray[1] = "not b anymore";
console.log(myArray);

// Add Items to an Array with push() and unshift()
function mixedNumbers(arr) {
  arr.unshift("I", 2, "three");
  arr.push(7, "VIII", 9);
  return arr;
}
console.log(mixedNumbers(["IV", 5, "six"]));

// Remove Items from an Array with pop() and shift()
function popShift(arr) {
  let popped = arr.pop();
  let shifted = arr.shift();
  return [shifted, popped];
}
console.log(popShift(["challenge", "is", "not", "complete"]));

// Remove Items Using splice()
const arr = [2, 4, 5, 1, 7, 5, 2, 1];
arr.splice(1, 4);
console.log(arr);

// Add Items Using splice()
function htmlColorNames(arr) {
  arr.splice(0, 2, "DarkSalmon", "BlanchedAlmond");
  return arr;
}
console.log(htmlColorNames(["DarkGoldenRod", "WhiteSmoke", "LavenderBlush", "PaleTurquoise", "FireBrick"]));

// Copy Array Items Using slice()
function forecast(arr) {
  return arr.slice(2, 4);
}
console.log(forecast(["cold", "rainy", "warm", "sunny", "cool", "thunderstorms"]));

// Copy an Array with the Spread Operator
function copyMachine(arr, num) {
  let newArr = [];
  while (num >= 1) {
    newArr.push([...arr]);
    num--;
  }
  return newArr;
}
console.log(copyMachine([true, false, true], 2));

// Combine Arrays with the Spread Operator
function spreadOut() {
  let fragment = ['to', 'code'];
  let sentence = ["learning", ...fragment, "is", "fun"];
  return sentence;
}
console.log(spreadOut());

// Check For The Presence of an Element With indexOf()
function quickCheck(arr, elem) {
  if (arr.indexOf(elem) >= 0) {
    return true;
  }
  return false;
}
console.log(quickCheck(['squash', 'onions', 'shallots'], 'mushrooms'));

// Iterate Through All an Array's Items Using For Loops
function filteredArray(arr, elem) {
  let newArr = [];
  for (let i = 0; i < arr.length; i++) {
    if (arr[i].indexOf(elem) === -1) {
      newArr.push(arr[i]);
    }
  }
  return newArr;
}
console.log(filteredArray([
  [3, 2, 3],
  [1, 6, 3],
  [3, 13, 26],
  [19, 3, 9]
], 3));

// Create complex multi-dimensional arrays
let myNestedArray = [
  // Only change code below this line
  ['unshift', false, 1, 2, 3, 'complex', 'nested'],
  [
    ['deep']
  ],
  [
    [
      ['deeper']
    ]
  ],
  [
    [
      [
        ['deepest']
      ]
    ]
  ]
  // Only change code above this line
];

// Add Key-Value Pairs to JavaScript Objects
let foods = {
  apples: 25,
  oranges: 32,
  plums: 28
};
foods.bananas = 13;
foods.grapes = 35;
foods.strawberries = 27;
console.log(foods);

// Modify an Object Nested Within an Object
let userActivity = {
  id: 23894201352,
  date: 'January 1, 2017',
  data: {
    totalUsers: 51,
    online: 42
  }
};
userActivity.data.online = 45;
console.log(userActivity);

// Access Property Names with Bracket Notation
let foods1 = {
  apples: 25,
  oranges: 32,
  plums: 28,
  bananas: 13,
  grapes: 35,
  strawberries: 27
};
function checkInventory(scannedItem) {
  return foods1[scannedItem];
}
console.log(checkInventory("apples"));

// Use the delete Keyword to Remove Object Properties
let foods2 = {
  apples: 25,
  oranges: 32,
  plums: 28,
  bananas: 13,
  grapes: 35,
  strawberries: 27
};
delete foods2.oranges;
delete foods2.plums;
delete foods2.strawberries;
console.log(foods2);

// Check if an Object has a Property
let users = {
  Alan: {
    age: 27,
    online: true
  },
  Jeff: {
    age: 32,
    online: true
  },
  Sarah: {
    age: 48,
    online: true
  },
  Ryan: {
    age: 19,
    online: true
  }
};
function isEveryoneHere(userObj) {
  if (
    userObj.hasOwnProperty("Alan") &&
    userObj.hasOwnProperty("Jeff") &&
    userObj.hasOwnProperty("Sarah") &&
    userObj.hasOwnProperty("Ryan")
  ) {
    return true;
  }
  return false;
}
console.log(isEveryoneHere(users));

// Iterate Through the Keys of an Object with a for...in Statement
let users1 = {
  Alan: {
    age: 27,
    online: false
  },
  Jeff: {
    age: 32,
    online: true
  },
  Sarah: {
    age: 48,
    online: false
  },
  Ryan: {
    age: 19,
    online: true
  }
};
function countOnline(usersObj) {
  let result = 0;
  for (let user in usersObj) {
    if (usersObj[user].online === true) {
      result++;
    }
  }
  return result;
}
console.log(countOnline(users1));

// Generate an Array of All Object Keys with Object.keys()
let users2 = {
  Alan: {
    age: 27,
    online: false
  },
  Jeff: {
    age: 32,
    online: true
  },
  Sarah: {
    age: 48,
    online: false
  },
  Ryan: {
    age: 19,
    online: true
  }
};

function getArrayOfUsers(usersObj) {
  return Object.keys(usersObj);
}
console.log(getArrayOfUsers(users2));

// Modify an Array Stored in an Object
let user = {
    name: "Kenneth",
    age: 28,
    data: {
        username: "kennethCodesAllDay",
        joinDate: "March 26, 2016",
        organization: "freeCodeCamp",
        friends: ["Sam", "Kira", "Tomo"],
        location: {
        city: "San Francisco",
        state: "CA",
        country: "USA"
        }
    }
    };
    function addFriend(userObj, friend) {
    userObj.data.friends.push(friend);
    return userObj.data.friends;
    }