implement array comprehension

README.md

@@ -45,9 +45,9 @@
 | [Computed property names](FEATURES.md#computed-property-names)       | ✓           |                       |
 | [Constants](FEATURES.md#constants)                                   | ✓           |                       |
 | [Binary and Octal Literals](FEATURES.md#binary-and-octal-literals)   | ✓           |                       |
-| [Iterators](FEATURES.md#iterators)                                   |             | ✓                     |
+| [Iterators](FEATURES.md#iterators)                                   | ✓           | ✓                     |
+| [Array comprehension](FEATURES.md#array-comprehension)               | ✓           |                       |
 | [Destructuring assignment](FEATURES.md#destructuring-assignment)     |             |                       |
-| [Array comprehension](FEATURES.md#array-comprehension)               |             |                       |
 | [Generators](FEATURES.md#generators)                                 |             |                       |
 
 ## Installation
@@ -157,6 +157,10 @@ browserify()
 
 Cannot subclass built-ins such as `Date`, `Array`, `DOM` etc.
 
+### Generator comprehension
+
+Not supported.
+
 ## Comparison to Traceur
 
 ### Performance

lib/6to5/templates/array-comprehension-container.js

@@ -0,0 +1,5 @@
+(function () {
+  var KEY = [];
+
+  return KEY;
+})();

lib/6to5/templates/array-comprehension-for-each.js

@@ -0,0 +1,3 @@
+OBJECT.forEach(function (KEY) {
+
+});

lib/6to5/templates/array-push.js

@@ -0,0 +1 @@
+KEY.push(STATEMENT);

lib/6to5/templates/if.js

@@ -0,0 +1,3 @@
+if (STATEMENT) {
+
+}

lib/6to5/transformers/array-comprehension.js

@@ -0,0 +1,55 @@
+var util = require("../util");
+
+exports.ComprehensionExpression = function (node, parent, opts, generateUid) {
+  var uid = generateUid("arr");
+
+  var container = util.template("array-comprehension-container", {
+    KEY: uid
+  });
+
+  var block = container.callee.body;
+  var body  = block.body;
+
+  var returnStatement = body.pop();
+
+  var build = function () {
+    var self = node.blocks.shift();
+    if (!self) return;
+
+    if (!self.of) {
+      throw util.errorWithNode(self, "for-in array comprehension is not supported");
+    }
+
+    var child = build();
+    if (!child) {
+      // last item
+
+      child = util.template("array-push", {
+        KEY: uid,
+        STATEMENT: node.body
+      }, true);
+
+      if (node.filter) {
+        var filter = util.template("if", {
+          STATEMENT: node.filter
+        });
+        filter.consequent.body = [child];
+        child = filter;
+      }
+    }
+
+    var container2 = util.template("array-comprehension-for-each", {
+      OBJECT: self.right,
+      KEY: self.left,
+    }, true);
+
+    container2.expression.arguments[0].body.body = [child];
+
+    return container2;
+  };
+
+  body.push(build());
+  body.push(returnStatement);
+
+  return container;
+};

test/fixtures/array-comprehension/if/actual.js

@@ -0,0 +1 @@
+var seattlers = [for (c of customers) if (c.city == "Seattle") { name: c.name, age: c.age }];

test/fixtures/array-comprehension/if/expected.js

@@ -0,0 +1,12 @@
+var seattlers = function () {
+  var _arr = [];
+  customers.forEach(function (c) {
+    if (c.city == "Seattle") {
+      _arr.push({
+        name: c.name,
+        age: c.age
+      });
+    }
+  });
+  return _arr;
+}();

test/fixtures/array-comprehension/multiple/actual.js

@@ -0,0 +1 @@
+var arr = [for (x of "abcdefgh".split("")) for (y of "12345678".split("")) (x + y)];

test/fixtures/array-comprehension/multiple/expected.js

@@ -0,0 +1,11 @@
+var arr = (function () {
+  var _arr = [];
+
+  "abcdefgh".split("").forEach(function (x) {
+    "12345678".split("").forEach(function (y) {
+      _arr.push(x + y);
+    });
+  });
+
+  return _arr;
+})();

test/fixtures/array-comprehension/no-in/actual.js

@@ -0,0 +1 @@
+var arr = [for (i in [1, 2, 3]) i * i];

test/fixtures/array-comprehension/no-in/options.json

@@ -0,0 +1,3 @@
+{
+  "throws": "for-in array comprehension is not supported"
+}

test/fixtures/array-comprehension/single/actual.js

@@ -0,0 +1 @@
+var arr = [for (i of [1, 2, 3]) i * i];

test/fixtures/array-comprehension/single/expected.js

@@ -0,0 +1,9 @@
+var arr = (function () {
+  var _arr = [];
+
+  [1, 2, 3].forEach(function (i) {
+    _arr.push(i * i);
+  });
+
+  return _arr;
+})();