Computer Science Lessons

data_types.md

Primitive Data Types

• Boolean (true, false)
• String ("asdf")
• Number
  • Integer (314)
  • Floating Point (3.14)
• Enum ({ A, B, C })

Abstract Data Types

• Array ([1,2,3])
• Key / Value
  • A Map
  • A Object / Object Literal (JavaScript)
  • An Associative Array (PHP)
  • A Dictionary (Python)
  • A Hash (Ruby)
  • In JSON:

    {
      "Key": "value"
    }

  • O(1)
• List
  • Meant to be iterated through
  • They can go in one direction or both (because they're a linear data type, you can only go in 2 possible directions)
  • .next(), .prev(), .val()
  • O(n)
• Set
  • Based on Maps
  • {1, 2, 3} <- A valid Set
  • {1, 2, 1, 2, 3} <- Not a valid, but it is what's known as a Bag or Multiset
    • What SQL queries return
• Queues and Stacks
  • Based on Lists
  • A queue is FIFO
  • A stack is LIFO
• Tree
  • They have branches
  • It's the highest order data structure that JSON can contain
  • Good for searches
  • How most filesystems are kept
  • Can be balanced or weighted
  • Can have Depth-First Search, Breadth-First Search
• Graph
  • Complex
  • Consist of Nodes / Vertices and Edges
  • Can describe relationships

json.md

Lesson

JSON Data Structures

{
  "key": "value",
  "object_key": {
    "name": "Nicole",
    "age": 27,
    "more_information": {
      "description": ""
    }
  },
  "array_key": [
    1.0,
    "string",
    2.9,
    "2.9.0",
    1
  ],
  "citiesAndZips": [
    {
      "city": "Denver",
      "zip": 80204
    },
    {
      "city": "Boulder",
      "zip": 80301
    },
    {
      "city": "Aurora",
      "zip": 80012
    },
    {
      "city": "Colorado Springs",
      "zip": 80000
    }
  ]
}

• Arrays have order
• Objects do not have order

Serialization

• JSON.stringify(obj);

'{"key":"value","object_key":{"name":"Nicole","age":27,"more_information":{"description":""}},"array_key":[1,"string",2.9,"2.9.0",1],"citiesAndZips":[{"city":"Denver","zip":80204},{"city":"Boulder","zip":80301},{"city":"Aurora","zip":80012},{"city":"Colorado Springs","zip":80000}]}'

JSON.parse('{"key":"value","object_key":{"name":"Nicole","age":27,"more_information":{"description":""}},"array_key":[1,"string",2.9,"2.9.0",1],"citiesAndZips":[{"city":"Denver","zip":80204},{"city":"Boulder","zip":80301},{"city":"Aurora","zip":80012},{"city":"Colorado Springs","zip":80000}]}');

Control Structures

for loop

for (var i = 0; i < obj.array_key.length; i++) {
  console.log(i, obj.array_key[i]);
}

• i++
  • Increments the i value
• for loops have three parts, separated by colons:
  • for (initial value; conditional which is evaluated each time; increment)

for in loop

for (var key in obj.object_key) {
  var val = obj.object_key[key];
  console.log(key);
  console.log(val);
}

Array Methods

• forEach(element, index)
• map(element, index, array)
• reduce(accumulator, key, val, array)
• filter(one, two)

Terminology

• REPL

Programming

• Procedural
• Object-oriented
• Functional
  • Immutability
  • No Side-effects