added example with subtyping arrays

javascript-fu/README.md

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+What NOT to do
+===
+
+These examples are for the purpose of explaining the stupid things people choose to do for idoitic reasons.
+
+There are also examples of things which are broken, but should have worked in a more ideal world.
+
+**NEVER USE THESE EXAMPLES IN REAL CODE**

javascript-fu/subclass-array.js

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+// Adapted from http://dean.edwards.name/weblog/2006/11/hooray/
+
+// Note: This examples works in browsers and SSJS. It won't work in MSIE.
+(function () {
+  "use strict";
+
+  // create the constructor
+  function FileList(args) {
+    var i;
+
+    if (!(args instanceof Array)) {
+      args = Array.prototype.slice.call(arguments);
+    }
+
+    // forEach won't work because `this` loses its scope
+    for (i = 0; i < args.length; i += 1) {
+      this.push(args[i]);
+    }
+
+    // prevent user extension
+    this.push = undefined;
+    this.pop = undefined;
+  };
+
+  // inherit from Array
+  FileList.prototype = new Array;
+
+  // add some sugar
+  FileList.prototype.item = function(index) {
+    return this[index];
+  };
+
+  // For some reason this won't stringify correctly
+  // as a subtype of Array
+  FileList.prototype.toJSON = function () {
+    return this.slice();
+  };
+
+  FileList.prototype.toString = function () {
+    return JSON.stringify(this.join(','));
+  };
+
+  module.exports = FileList;
+}());
+
+
+// Test functionality of the above
+(function () {
+  "use strict";
+
+  var FileList = module.exports
+    , fileList
+    ;
+
+  // First of all: JavaScript doesn't have arrays. Really!
+  // http://javascript.about.com/od/problemsolving/a/notarrays.htm
+
+  // NOTE: .length will only be correct if .push is used
+  // not if [i] notation is used
+  /*
+  var fileList = new FileList();
+  fileList.push('a');
+  fileList.push('b');
+  fileList.push('c');
+  */
+
+  fileList = new FileList(['a','b',3]);
+  console.error('[FAIL]', 'Array.isArray(fileList):', Array.isArray(fileList));
+
+  console.log(fileList.item(0));
+  console.log(fileList[1]);
+
+  fileList = new FileList('a','b',3);
+  console.log(fileList.item(2));
+
+  // Love the brokenness
+  console.log(JSON.stringify(['a', 'b', 3]));
+  //console.log(fileList.toString());
+  console.log([1, 2, 3].toString());
+  console.log(JSON.stringify(fileList), typeof JSON.stringify(fileList));
+  console.log(fileList.forEach)
+}());