js 编写一个神奇的四则运算

2018/03/06 19:06
阅读数 19

写一个算法,有时候可以用简单的方法就可以写出来,但是只能针对特定的环境,如果要能够适应不同的环境,就需要对算法进行优化,在优化的过程中,你会觉得非常神奇,下面来看一个简单的四则运算的算法编写方式:

1.简单粗暴的实现:直接创建一个对象,在对象上直接挂载加减乘除方法

 1  <script>
 2         var per = {
 3             add: function(n1, n2) {
 4                 return n1 + n2;
 5             },
 6             sbb: function(n1, n2) {
 7                 return n1 - n2;
 8             },
 9             multi: function(n1, n2) {
10                 return n1 * n2;
11             },
12             div: function(n1, n2) {
13                 return n1 / n2;
14             },
15 
16         }
17         console.log(per.add(10, 20));
18         console.log(per.sbb(10, 20));
19         console.log(per.multi(10, 20));
20         console.log(per.div(10, 20));
21     </script>

运行结果:

2.采用构造函数的方式,把方法加减乘除方法写在构造函数中

 1 <script>
 2         function OPP(n1, n2) {
 3             this.num1 = n1 || 0; // 当传入参数n1时,设置this.num1 = n1,否则设置为0;
 4             this.num2 = n2 || 0; // 当传入参数n2时,设置this.num2 = n2,否则设置为0;
 5             this.setdata = function(n1, n2) {
 6                 this.num1 = n1 || 0; // 当传入参数n1时,设置this.num1 = n1,否则设置为0;
 7                 this.num2 = n2 || 0; // 当传入参数n2时,设置this.num2 = n2,否则设置为0;
 8             };
 9             // 函数的运行,首先设置相关元素的属性值,然后再进行调用
10             this.add = function() {
11                 // 当add()函数传入参数时,那么设置参数就使用传入的参数arguments[0]/arguments[1],否则使用原先的构造函数的参数this.num1/this.num2
12                 this.setdata(arguments[0] || this.num1, arguments[1] || this.num2);
13                 return this.num1 + this.num2;
14             };
15             this.sbb = function() {
16                 this.setdata(arguments[0] || this.num1, arguments[1] || this.num2);
17                 return this.num1 - this.num2;
18             };
19             this.multi = function() {
20                 this.setdata(arguments[0] || this.num1, arguments[1] || this.num2);
21                 return this.num1 * this.num2;
22             };
23             this.div = function() {
24                 this.setdata(arguments[0] || this.num1, arguments[1] || this.num2);
25                 return this.num1 / this.num2;
26             }
27         }
28         console.log(new OPP(10, 20).add()); // 30
29         console.log(new OPP().add(10, 20)); // 30
30         console.log(new OPP(100, 200).add(10, 20)); //30
31         console.log(new OPP(10, 20).sbb()); //-10
32         console.log(new OPP().sbb(10, 20)); //-10
33         console.log(new OPP(100, 200).sbb(10, 20)); //-10
34         console.log(new OPP(10, 20).multi()); //200
35         console.log(new OPP().multi(10, 20)); //200
36         console.log(new OPP(10, 20).div()); //0.5
37         console.log(new OPP().div(10, 20)); //0.5
38     </script>

运行结果:

3. 采用构造函数的原型对象的方式,即将调用函数挂载到了构造函数的原型对象上,当调用函数时,是通过原型链进行调用的,而上一个没有涉及到原型链的问题,这是与上一种方式的本质区别

 1 <script>
 2         function OPP(n1, n2) {
 3             this.num1 = n1 || 0; // 当传入参数n1时,设置this.num1 = n1,否则设置为0;
 4             this.num2 = n2 || 0; // 当传入参数n2时,设置this.num2 = n2,否则设置为0;
 5         }
 6         OPP.prototype = {
 7             constructor: OPP,
 8             setdata: function(n1, n2) {
 9                 this.num1 = n1 || 0;
10                 this.num2 = n2 || 0;
11             },
12             add: function() {
13                 this.setdata(arguments[0] || this.num1, arguments[1] || this.num2);
14                 return this.num1 + this.num2;
15             },
16             sbb: function() {
17                 this.setdata(arguments[0] || this.num1, arguments[1] || this.num2);
18                 return this.num1 - this.num2;
19             },
20             multi: function() {
21                 this.setdata(arguments[0] || this.num1, arguments[1] || this.num2);
22                 return this.num1 * this.num2;
23             },
24             div: function() {
25                 this.setdata(arguments[0] || this.num1, arguments[1] || this.num2);
26                 return this.num1 / this.num2;
27             },
28         };
29 
30         console.log(new OPP(10, 20).add()); // 30
31         console.log(new OPP().add(10, 20)); // 30
32         console.log(new OPP(100, 200).add(10, 20)); //30
33         console.log(new OPP(10, 20).sbb()); //-10
34         console.log(new OPP().sbb(10, 20)); //-10
35         console.log(new OPP(100, 200).sbb(10, 20)); //-10
36         console.log(new OPP(10, 20).multi()); //200
37         console.log(new OPP().multi(10, 20)); //200
38         console.log(new OPP(10, 20).div()); //0.5
39         console.log(new OPP().div(10, 20)); //0.5
40     </script>

运行结果:

4. 使用继承的方式实现:

 1 <script>
 2         function OPP(n1, n2) {
 3             this.num1 = n1 || 0; // 当传入参数n1时,设置this.num1 = n1,否则设置为0;
 4             this.num2 = n2 || 0; // 当传入参数n2时,设置this.num2 = n2,否则设置为0;
 5         };
 6         OPP.prototype.run = function() {
 7             throw new Error('原型链中没有该方法,请从写该方法才能调用!');
 8         };
 9 
10         function object(o) {
11             var G = function() {};
12             G.prototype = o;
13             return new G();
14         };
15 
16         function inheritPrototype(subObj, superObj) {
17             //调用中间函数:object,实现把子类的原型对象指向中间函数G的实例,而G的实例指向想父类的原型对象,
18             // 同时把实例的constructor 属性指向子类;相当于在原型链中增加了一个实例,而实例作为子类的原型对象,这样子类就可以通过原型链实现对父类的继承了
19             var proObj = object(superObj.prototype);
20             // 调用object()函数的意义,基本上就是实现以下注释的功能
21             // var G = function() {};
22             // G.prototype = superObj.prototype;
23             // var proObj = new G();
24             proObj.constructor = subObj;
25             subObj.prototype = proObj;
26         };
27 
28         function add(n1, n2) {
29             OPP.call(this, n1, n2);
30         };
31         inheritPrototype(add, OPP);
32         add.prototype.run = function() {
33             return this.num1 + this.num2;
34         };
35 
36         function sbb(n1, n2) {
37             OPP.call(this, n1, n2);
38         };
39         inheritPrototype(sbb, OPP);
40         sbb.prototype.run = function() {
41             return this.num1 - this.num2;
42         };
43 
44         function multi(n1, n2) {
45             OPP.call(this, n1, n2);
46         };
47         inheritPrototype(multi, OPP);
48         multi.prototype.run = function() {
49             return this.num1 * this.num2;
50         };
51 
52         function div(n1, n2) {
53             OPP.call(this, n1, n2);
54         };
55         inheritPrototype(div, OPP);
56         div.prototype.run = function() {
57             return this.num1 / this.num2;
58         };
59 
60         var huanying2015 = function(n1, n2, oper) {
61             switch (oper) {
62                 case '+':
63                     return new add(n1, n2).run();
64                     break;
65                 case '-':
66                     return new sbb(n1, n2).run();
67                     break;
68                 case '*':
69                     return new multi(n1, n2).run();
70                     break;
71                 case '/':
72                     return new div(n1, n2).run();
73                     break;
74             }
75         }
76 
77         console.log(huanying2015(100, 200, '+'));
78         console.log(huanying2015(100, 200, '-'));
79         console.log(huanying2015(100, 200, '*'));
80         console.log(huanying2015(100, 200, '/'));
81     </script>

 

运行结果:

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