C４物件

前面我們學到的ＩＦ ＦＯＲ 等等沒有物件的程式稱作結構式程式語言，物件的誕生改變了程式的生態

物件的概念可以從上一章說到的字典講起，物件本身附帶函數，資料與函數結合在一起。

1.請寫出一個具有加減運算的複數物件？ (Complex, add, sub)

class complex{
    constructor (r,i){
        this.r=r;
        this.i=i;
    }
}

add(c2){
    return new complex(this.r+c2.r,this.i+c2.i);
}
sub{
    return new complex(this.r-c2.r,this.i-c2.i); 
}

`

3.請寫一組物件，包含《矩形、圓形》與抽象的形狀，每個物件都具有 area() 函數可以計算其面積？ (Shape.area(), Rectangle, Circle)

//請寫一組物件，包含《矩形、圓形》與抽象的形狀，每個物件都具有 area() 函數可以計算其面積？ (Shape.area(), Rectangle, Circle)

"use strict"

class Shape{
    constructor(Length,Width,r){
        this.Length=Length;
        this.Width=Width;
        this.r=r;
    }

    AreaOfRec(){
    return this.Length*this.Width;
    }
    AreaOfCircle(){
    return this.r*this.r*Math.PI;
    }
}

var R1= new Shape(5,6,0);
var C1= new Shape(0,0,9);
var R2= new Shape(2,2);
var C2= new Shape(0,0,3);
console.log("the Length of R1=",+R1.Length);
console.log("the Width of R1=",+R1.Width);
console.log("the r of R1=",+R1.r);
console.log("the area of R1=",+R1.AreaOfRec());

console.log("the Length of C1=",+C1.Length);
console.log("the Width of C1=",+C1.Width);
console.log("the r of C1=",+C1.r);
console.log("the area of C1=",+C1.AreaOfCircle());

console.log("the Length of R2=",+R2.Length);
console.log("the Width of R2=",+R2.Width);
console.log("the r of R2=",+R2.r);
console.log("the area of R2=",+R2.AreaOfRec());

console.log("the Length of C2=",+C2.Length);
console.log("the Width of C2=",+C2.Width);
console.log("the r of C2=",+C2.r);
console.log("the area of C2=",+C2.AreaOfCircle());

`

我一開始是使用var R1=shape.constructor()

可是執行時電腦和我說 這不是一個function

於是徂善如流使用ＮＥＷ的做法

除此此外，我還想要讓物件能夠辨識自己的形狀。這樣比較有趣

"use strict"

class Shape{
    constructor(Length,Width,r){
        this.Length=Length;
        this.Width=Width;
        this.r=r;
    }
    theShapeType(){
    if (this.Length>0&&this.Width>0&&this.r===0){
        return "Rectangle"
    }
    else if (this.Length===0&&this.Width===0&&this.r>0){
        return "Circle"
    }
    else{
        return "It is not a shape inculded in this Object" 
    }
    }
    AreaOfRec(){
    return this.Length*this.Width;
    }
    AreaOfCircle(){
    return this.r*this.r*Math.PI;
    }
}

var R1= new Shape(5,6,0);
var C1= new Shape(0,0,9);
var R2= new Shape(2,2);
var C2= new Shape(0,0,3);
console.log("the Length of R1=",+R1.Length);
console.log("the Width of R1=",+R1.Width);
console.log("the r of R1=",+R1.r);
console.log("the area of R1=",+R1.AreaOfRec());
console.log("the shape of R1=",+R1.theShapeType());

console.log("the Length of C1=",+C1.Length);
console.log("the Width of C1=",+C1.Width);
console.log("the r of C1=",+C1.r);
console.log("the area of C1=",+C1.AreaOfCircle());
console.log("the shape of C1=",+C1.theShapeType());

console.log("the Length of R2=",+R2.Length);
console.log("the Width of R2=",+R2.Width);
console.log("the r of R2=",+R2.r);
console.log("the area of R2=",+R2.AreaOfRec());
console.log("the shape of R2=",+R2.theShapeType());

console.log("the Length of C2=",+C2.Length);
console.log("the Width of C2=",+C2.Width);
console.log("the r of C2=",+C2.r);
console.log("the area of C2=",+C2.AreaOfCircle());
console.log("the shape of C2=",+C2.theShapeType());

但是不知道為什麼，輸出之後，形狀的部分是NaN

問了老師以後發現．．．．．

原來問題出在符號的使用

console.log("the shape of R1=",+R1.theShapeType()); // 這是錯的 

console.log("the shape of R1="+R1.theShapeType()); // 這是才是對的 

console.log("the shape of R1=",R1.theShapeType()); // 或者是這樣

看出來問題在哪裡了嗎？

問題在於“,”與“+”很容易發生問題

電腦可能會以為 我是要“加”上某個東西

所以產生了ＮaN

因為我想輸出的形狀型態是用字串表達的

但是字串不是一個數字

我想這也解釋了為什麼除了形狀之外的東西都不會遇到這個問題

以下是正確的版本

"use strict"

class Shape{
    constructor(Length,Width,r){
        this.Length=Length;
        this.Width=Width;
        this.r=r;
    }
    theShapeType(){
    if (this.Length>0&&this.Width>0&&this.r===0){
        return "Rectangle"
    }
    else if (this.Length===0&&this.Width===0&&this.r>0){
        return "Circle"
    }
    else{
        return "It is not a shape inculded in this Object" 
    }
    }
    AreaOfRec(){
    return this.Length*this.Width;
    }
    AreaOfCircle(){
    return this.r*this.r*Math.PI;
    }
}

var R1= new Shape(5,6,0);
var C1= new Shape(0,0,9);
var R2= new Shape(2,2);
var C2= new Shape(0,0,3);
console.log("the Length of R1="+R1.Length);
console.log("the Width of R1="+R1.Width);
console.log("the r of R1="+R1.r);
console.log("the area of R1="+R1.AreaOfRec());
console.log("the shape of R1="+R1.theShapeType());

console.log("the Length of C1="+C1.Length);
console.log("the Width of C1="+C1.Width);
console.log("the r of C1="+C1.r);
console.log("the area of C1="+C1.AreaOfCircle());
console.log("the shape of C1="+C1.theShapeType());

console.log("the Length of R2="+R2.Length);
console.log("the Width of R2="+R2.Width);
console.log("the r of R2="+R2.r);
console.log("the area of R2="+R2.AreaOfRec());
console.log("the shape of R2="+R2.theShapeType());

console.log("the Length of C2="+C2.Length);
console.log("the Width of C2="+C2.Width);
console.log("the r of C2="+C2.r);
console.log("the area of C2="+C2.AreaOfCircle());
console.log("the shape of C2="+C2.theShapeType());