FCC:Object Oriented and Functional Programming (2 hours)面向对象的函数设计法

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2016.10.28 8：30启动

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Declare JavaScript Objects as Variables 将对象设为变量

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

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Construct JavaScript Objects with Functions 用构造函数创建对象

this

• A constructor function is given a capitalized name to make it clear that it is a constructor.【构造函数的变量名必须大写，区别其是构造器constructor】
• a constructor as a description for the object it will create.构造器是对象的一种新类型 this.wheels = 4;
• 注意性质的分隔符号：；

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

呼出构造函数的对象

• 赋予一个函数一个构造函数对象 ：var myCar = new Car();，其中new必不可少；
• 该变量就相当于一个对象名，可以进行有关的任何操作，如：myCar.nickname = "xiaobai";

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

// Only change code below this line.

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

运行结果：

通过parameters 元素修改对象性质的值

• 就是将固定值变为函数的元素变量，然后在（）里添加修改后值

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(8,9,10);

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this

Make Object Properties Private 创建对象的秘密性质

• 关于public properties 与 private properties的区别:
  1. 公共性质可以被外界呼出修改，秘密性质无法修改；
  2. 可以通过直接修改公共性质间接修改秘密性质；
• 例子：设定汽车的速度，但外界不能直接修改速度，只能通过加速或者减速来影响速度，此时汽车速度则为秘密性质，减速减速的改变则为可以直接修改的公共性质。

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;
  };
};

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Iterate over Arrays with map 用map历遍数组（对数组中所有元素执行同一操作）

• 注意（）以及{}的相对位置，以及相当容易遗漏的map()后的;

var oldArray = [1, 2, 3];
var timesFour = oldArray.map(function(val){
  return val * 4;
});
console.log(timesFour); // returns [4, 8, 12]
console.log(oldArray);  // returns [1, 2, 3]

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Condense arrays with reduce 用reduce压缩数组

The array method reduce is used to iterate through an array and condense it into one value.【将数组中元素压缩成一个数】

• 与map的不同：map对各个元素操作，结果是一个数组，reduce的结果是一个值
• 可看作数组元素的累加减乘除器
• 修改var singleVal = 2;的值无影响，修改reduce的后面的0有影响，因为reduce对前者覆盖，而后者是与function 的结果想加，可看作初值

var array = [4,5,6,7,8];
var singleVal = 2;

// Only change code below this line.

var singleVal = array.reduce(function(previousVla,currentVla){
  return previousVla + currentVla;
},0);

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Filter Arrays with filter 用fliter过滤数组元素（筛选）

• fliter

array = array.filter(function(val) {
  return val !== 5;
});

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17

Sort Arrays with sort 用sort排列数组内的元素

• a-b 从小到大，b-a从大到小

• 原理还不甚明了

var array = [1, 12, 21, 2];
array.sort(function(a, b) {
  return b - a ;
});

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Reverse Arrays with reverse 用reverse对调数组

• 对调数组内元素的顺序，与元素的大小无关

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

// Only change code below this line.

newArray = array.reverse();

结果

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Concatenate Arrays with concat 用 contat 连接数组

• newArray = oldArray.concat(otherArray);
• 注意是concat 不是cantat或者contact

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

var concatMe = [4,5,6];

// Only change code below this line.

newArray = oldArray.concat(concatMe);

运行结果
[1,2,3,4,5,6]

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Split Strings with split 用split分开字符串形成数组

• var array = string.split('s'); s是标记字符，示例中是空格
• 注意（）中是''不是“”

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

// Only change code below this line.

array = string.split(' ');

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Join Strings with join 用join连接数组元素成字符串，split的逆运算

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

// Only change code below this line.

joinedString = joinMe.join(' ');

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2016.10.28 10：40 END

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TOTAL ：2h10min