├── README.md
└── jsPipe.js


/README.md:
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 1 | Implementing pipes in Javascript using pseudo operator overloading.
 2 | ======
 3 | Most of the credit goes to Dr. Axel Rauschmayer that introduced me to the concept of pseudo operator overloading in Javascript in his [great article](http://www.2ality.com/2011/12/fake-operator-overloading.html?m=1) about the subject.
 4 | 
 5 | The code it self is pretty simple (containing just 28 lines of Javascript for the actual pipe implementation).
 6 | 
 7 | I have used the fact that when doing operations on Objects, the method valueOf of the Object is being triggered.
 8 | Using a bit of trickery, (and overwriting primitive prototypes) I was able to go as far as to make the following work and produce the expected result:
 9 |  ```javascript
10 | var result;
11 | p([1,6,4,9,3])
12 |  | sort
13 |  | removeLessThenThree
14 |  | doubleAll
15 |  | print // prints [8, 12, 18]
16 |  | function (value) { result = value; }
17 |  |pe
18 | ```
19 | 
20 | This little trick is obviously not suitable for real usage, but it is a great example of Javascript's hidden flexibility.
21 | 
22 | 


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/jsPipe.js:
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 1 | var p = (function (exports) {
 2 | 
 3 |     var pipedValue,
 4 |         pipes = [],
 5 |         addToPipe = false,
 6 |         runPipe = function () {
 7 |             var val = pipedValue, idx;
 8 |             for (idx in pipes) {
 9 |                 val = pipes[idx](val);
10 |             }
11 |             pipes = [];
12 |             addToPipe = false;
13 | 
14 |             return;
15 |         };
16 | 
17 |     Function.prototype.valueOf  = function () {
18 |         return addToPipe ? pipes.push(this) : this;
19 |     };
20 | 
21 |     exports.pe = {valueOf: runPipe};
22 | 
23 |     return function (newPipedValue) {
24 |         addToPipe = true;
25 |         pipedValue = newPipedValue;
26 |     };
27 | 
28 | }(window));
29 | 
30 | 
31 | function sort(array) {
32 |     return Array.prototype.sort.apply(array);
33 | }
34 | 
35 | function removeLessThenThree(array) {
36 |     return Array.prototype.filter.apply(array, [
37 |             function (n) { return n > 3; }
38 |         ]);
39 | }
40 | 
41 | function doubleAll(array) {
42 |     return array.map(function(n) { return n*2; } );
43 | }
44 | 
45 | function print(value) {
46 |     console.log(value);
47 | }
48 | 
49 | var result;
50 | p([1,6,4,9,3])
51 |  | sort
52 |  | removeLessThenThree
53 |  | doubleAll
54 |  | print
55 |  | function (value) { result = value; }
56 |  |pe
57 | 
58 | 
59 | 


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