Object Oriented and Functional Programming

1-Declare JavaScript Objects as Variables

var car = {
  "wheels":4,
  "engines":1,
  "seats":5
};

var motorBike = {
  "wheels":3,
  "engines":1,
  "seats":2,

  // Only change code below this line.

};

2-Construct JavaScript Objects with Functions

• 構造函數通常第一個字大寫，用來區分一般函數

• this 指向創建出來的對象

var Car = function() {
  this.wheels = 4;
  this.engines = 1;
  this.seats = 5;
};

// Only change code below this line.

var MotorBike = function() {
  this.engines=1;
  this.wheels=2;
  this.seats=2;
};

3-Make Instances of Objects with a Constructor Function

• 用 new function() 來創建一個實力 instance

var Car = function() {
  this.wheels = 4;
  this.engines = 1;
  this.seats = 5;
};

// Only change code below this line.

var myCar = new Car();
myCar.nickname = "Chacha";

4-Make Unique Objects by Passing Parameters to our Constructor

var Car = function(wheels, seats, engines) {
  //Change this constructor
  this.wheels = wheels;
  this.seats = seats;
  this.engines = engines;
};

//Try it out here
var myCar = new Car(2, 2, 1) ;

5-Make Object Properties Private

• 建構函數內，自己的函數稱為方法，自己的特徵稱作屬性(忘了)

• 讓私有資料只能透過方法存取

var Car = function() {
  // this is a private variable
  var speed = 10;

  // these are public methods
  this.accelerate = function(change) {
    speed += change;
  };

  this.decelerate = function() {
    speed -= 5;
  };

  this.getSpeed = function() {
    return speed;
  };
};

var Bike = function() {

  // Only change code below this line.
  var gear = 2;

  this.getGear = function(){
    return gear;
  };

  this.setGear = function(change){
    gear = change;
    return gear;
  };

};

var myCar = new Car();

var myBike = new Bike();
myBike.getGear(3);

6-Iterate over Arrays with map

• 有點詭異的迴圈

• .map() 括號中是個 callback function

• 第一個參數是處理的元素，第二個是 index，第三個是陣列

• 好吧其實我看不太懂

• https://developer.mozilla.org/zh-TW/docs/Web/JavaScript/Reference/Global_Objects/Array/map

• http://fred-zone.blogspot.tw/2017/01/javascript-mapreduce.html

var oldArray = [1,2,3,4,5];

// Only change code below this line.

var newArray = oldArray.map(function(val){
 return val+3; 
}
);

7-Condense arrays with reduce

• 將陣列變成一個數字

• reduce() 有兩個參數

• 第一個，callback function 有兩個參數，累加器和當前值

• 第二個，是初始值

var array = [4,5,6,7,8];
var singleVal = 0;

// Only change code below this line.

singleVal = array.reduce(function(previousVal, currentVal){
  return previousVal+currentVal;
},0);

8-Filter Arrays with filter

var oldArray = [1,2,3,4,5,6,7,8,9,10];

// Only change code below this line.

var newArray = oldArray.filter(function(val){
  return val<6;
});

9-Sort Arrays with sort

• a-b 是正序排

• b-a 是逆序排

var array = [1, 12, 21, 2];

// Only change code below this line.

array.sort(function(a, b){
  return b-a;
});

10-Reverse Arrays with reverse

var array = [1,2,3,4,5,6,7];
var newArray = [];

// Only change code below this line.

newArray = array.reverse();

11-Concatenate Arrays with concat

var oldArray = [1,2,3];
var newArray = [];

var concatMe = [4,5,6];

// Only change code below this line.

newArray = oldArray.concat(concatMe);

• delimiter 分隔符號

12-Split Strings with split

var string = "Split me into an array";
var array = [];

// Only change code below this line.

array = string.split(' ');

13-Join Strings with join

var joinMe = ["Split","me","into","an","array"];
var joinedString = '';

// Only change code below this line.

joinedString = joinMe.join(" ");