Dean Edwards 写的强大的forEach

http://dean.edwards.name/

主要代码：

 1 // array-like enumeration
 2 if (!Array.forEach) { // mozilla already supports this
 3     Array.forEach = function(array, block, context) {
 4         for (var i = 0; i < array.length; i++) {
 5             block.call(context, array[i], i, array);
 6         }
 7     };
 8 }
 9 
10 // generic enumeration
11 Function.prototype.forEach = function(object, block, context) {
12     for (var key in object) {
13         if (typeof this.prototype[key] == "undefined") {
14             block.call(context, object[key], key, object);
15         }
16     }
17 };
18 
19 // character enumeration
20 String.forEach = function(string, block, context) {
21     Array.forEach(string.split(""), function(chr, index) {
22         block.call(context, chr, index, string);
23     });
24 };
25 
26 // globally resolve forEach enumeration
27 var forEach = function(object, block, context) {
28     if (object) {
29         var resolve = Object; // default
30         if (object instanceof Function) {
31             // functions have a "length" property
32             resolve = Function;
33         } else if (object.forEach instanceof Function) {
34             // the object implements a custom forEach method so use that
35             object.forEach(block, context);
36             return;
37         } else if (typeof object == "string") {
38             // the object is a string
39             resolve = String;
40         } else if (typeof object.length == "number") {
41             // the object is array-like
42             resolve = Array;
43         }
44         resolve.forEach(object, block, context);
45     }
46 };

下面是测试代码：

 1 function print(value, key, object, tag) {
 2 
 3           if (!tag) tag = "PRE";
 4 
 5         document.write("<" + tag + ">" + key + ": " + value + "</" + tag + ">");
 6 
 7       };
 8 
 9       
10 
11       print('"abc"', "forEach", null, "h3");
12 
13       forEach ("abc", print);
14 
15       
16 
17       print("[1, 2, 3]", "forEach", null, "h3");
18 
19       forEach ([1, 2, 3], print);
20 
21       
22 
23       print("{a:1, b:2, c:3}", "forEach", null, "h3");
24 
25       forEach ({a:1, b:2, c:3}, print);
26 
27       
28 
29       print("arguments(1, 2, 3)", "forEach", null, "h3");
30 
31       function test() {
32 
33           forEach (arguments, print);
34 
35       };
36 
37       test(1, 2, 3);
38 
39       
40 
41       print("fred", "forEach", null, "h3");
42 
43       function Person(name, age) {
44 
45           this.name = name || "";
46 
47           this.age = age || 0;
48 
49       };
50 
51       Person.prototype = new Person;
52 
53       Person.LATIN = "Homo Sapiens";
54 
55       var fred = new Person("Fred", 38);
56 
57       fred.language = "English";
58 
59       fred.wife = "Wilma";
60 
61       forEach (fred, print);
62 
63       
64 
65       print("fred", "Person.forEach", null, "h3");
66 
67       Person.forEach (fred, print);
68 
69       
70 
71       print("Person", "forEach", null, "h3");
72 
73       forEach (Person, print);