Object、Array、Vector遍历性能测试

破晓

talk is cheap，show me the code！

1. var obj:Object = { };
   
2. var arrVector:Vector.<int> = new Vector.<int>();
   
3. var arrArray:Array = [];
   
4. 
   
5. var len:int;
   
6. var i:int;
   
7. var key:String;
   
8. var val:int;
   
9. var t1:int, t2:int, t3:int, t4:int, t5:int, t6:int, t7:int, t8:int, t9:int,t10:int;
   
10. var t11:int, t12:int, t13:int, t14:int, t15:int, t16:int, t17:int, t18:int, t19:int;
    
11. 
    
12. //初始化50万个元素
    
13. t1 = getTimer();
    
14. for (i = 0; i < 500000; i++)  
    
15. {
    
16.     obj[i] = i;
    
17.     arrVector.push(i);
    
18.     arrArray.push(i);
    
19. }
    
20. //for遍历key
    
21. t2 = getTimer();
    
22. for (key in obj)
    
23. {
    
24.     val = obj[key];
    
25. }
    
26. //for each 遍历value
    
27. t3 = getTimer();
    
28. for each(val in obj)
    
29. {
    
30.     val;
    
31. }
    
32. //for each 遍历Vector
    
33. t4 = getTimer();
    
34. for each(val in arrVector)
    
35. {
    
36.     val;
    
37. }
    
38. //for循环Vector，length属性放for里面
    
39. t5 = getTimer();
    
40. for (i = 0; i < arrVector.length; i++)  
    
41. {
    
42.     val = arrVector[i];
    
43. }
    
44. //for循环Vector，length属性放for外面
    
45. t6 = getTimer();
    
46. len = arrVector.length;
    
47. for (i = 0; i < len; i++)  
    
48. {
    
49.     val = arrVector[i];
    
50. }
    
51. //for each遍历Vector
    
52. t7 = getTimer();
    
53. for each(val in arrVector)
    
54. {
    
55.     val;
    
56. }
    
57. //for循环Array，length属性放for里面
    
58. t8 = getTimer();
    
59. for (i = 0; i < arrArray.length; i++)  
    
60. {
    
61.     val = arrArray[i];
    
62. }
    
63. //for循环Array，length属性放for外面
    
64. t9 = getTimer();
    
65. len = arrArray.length;
    
66. for (i = 0; i < len; i++)  
    
67. {
    
68.     val = arrArray[i];
    
69. }
    
70. t10 = getTimer();
    
71. 
    
72. trace("1:" + (t2-t1));//288
    
73. trace("2:" + (t3-t2));//1974
    
74. trace("3:" + (t4-t3));//67
    
75. trace("4:" + (t5-t4));//50
    
76. trace("5:" + (t6-t5));//44
    
77. trace("6:" + (t7-t6));//42
    
78. trace("7:" + (t8-t7));//52
    
79. trace("8:" + (t9-t8));//70
    
80. trace("9:" + (t10-t9));//46

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可以看出for遍历object获得key，然后再用obj[key]获得value的方式性能是最低的！

用Vector，然后把length提前赋值出来，再for循环是最快的!

补充：根据这篇文章（jacksondunstan.com/articles/2514）的测试结果，在使用for in循环时，不指定key的类型，比定义string类型的key，快5倍：

1. // 慢！
   
2. for (var str:String in obj)
   
3. {
   
4. }
   
5.   
   
6. // 比上面那种方式快 5 倍！
   
7. for (var key:* in obj)
   
8. {
   
9. }

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作者：YoYo，原文地址：http://yoyo.play175.com/p/202.html