高效图形（一）

 1 var Pet = function(name, legs){
 2     this.name = name;
 3     this.legs = legs;
 4 };
 5 Pet.prototype.getDetails = function(){
 6     return this.name + " has " + this.legs + " legs";
 7 };
 8 
 9 var Cat = function(name){
10     Pet.call(this, name, 4);// Call the parent object's constructor
11 };
12 Cat.prototype = new Pet();
13 
14 Cat.prototype.action = function(){
15     return "Catch a bird";
16 };
17 
18 // create an instance of Cat in petCat
19 var petCat = new Cat('Flex');
20 
21 var details = petCat.getDetails();
22 console.log("details:", details);
23 var action = petCat.action();
24 console.log("action: " , action)
25 console.log("petCat.name, petCat.legs: ", petCat.name, petCat.legs)
26 petCat.name = 'Sylvester';
27 petCat.legs = 7;
28 console.log("petCat.name, petCat.legs:",petCat.name, petCat.legs)
29 details = petCat.getDetails();
30 console.log("details::", details)
31 
32 //  这种继承方法没有提供对外部继承的保护，在涉及多个程序的复杂项目中这个缺点也许会影响很大。
33 //  另一个选项无需使用prototype 或new,而是利用javascript的“函数继承”特性来吸收和增强对象实例。

 1 var pet = function(name, legs){
 2             var that = {
 3                 name : name,
 4                 getDetails : function(){
 5                     return that.name + " has " + legs + " legs";
 6                 }
 7             };
 8                 return that;
 9         };
10 
11         var cat = function(name){
12             var that = pet(name, 4);
13 
14             that.action = function(){
15                 return 'Cathch a bird!';
16             };
17 
18             return that;
19         };
20 
21 
22         var petCat2 = cat('Flexi');
23         console.log(petCat2);
24 
25         details = petCat2.getDetails();
26         console.log("details:", details);
27 
28         action = petCat2.action();
29         console.log("action:", action);
30 
31         petCat2.name = 'Nick';
32         console.log("name:::",petCat2.name);
33         petCat2.legs = 7;
34         console.log("legs:",petCat2.legs)
35         details = petCat2.getDetails();
36         console.log("details::", details)

 1 var startTime = new Date().getTime();
 2 for(var i = 0; i < 1000; i++){
 3     pice();
 4     var  time = new Date().getTime() - startTime;
 5     console.log(time);
 6 }
 7 
 8 var fastSin = function(steps){
 9     var table = [],
10         ang = 0,
11         angStep = (Math.PI * 2) / steps;
12     do{
13         table.push(Math.sin(ang));
14         ang += angStep;
15     }while(ang < Math.PI * 2);
16     return table;
17 };