Implement {map,set}.{size,empty}. Fixes #1648.

d3.js

@@ -276,12 +276,17 @@ d3 = function() {
       });
       return entries;
     },
+    size: function() {
+      var size = 0;
+      for (var key in this) if (key.charCodeAt(0) === d3_map_prefixCode) ++size;
+      return size;
+    },
+    empty: function() {
+      for (var key in this) if (key.charCodeAt(0) === d3_map_prefixCode) return false;
+      return true;
+    },
     forEach: function(f) {
-      for (var key in this) {
-        if (key.charCodeAt(0) === d3_map_prefixCode) {
-          f.call(this, key.substring(1), this[key]);
-        }
-      }
+      for (var key in this) if (key.charCodeAt(0) === d3_map_prefixCode) f.call(this, key.substring(1), this[key]);
     }
   });
   var d3_map_prefix = "\x00", d3_map_prefixCode = d3_map_prefix.charCodeAt(0);
@@ -373,12 +378,17 @@ d3 = function() {
       });
       return values;
     },
+    size: function() {
+      var size = 0;
+      for (var value in this) if (value.charCodeAt(0) === d3_map_prefixCode) ++size;
+      return size;
+    },
+    empty: function() {
+      for (var value in this) if (value.charCodeAt(0) === d3_map_prefixCode) return false;
+      return true;
+    },
     forEach: function(f) {
-      for (var value in this) {
-        if (value.charCodeAt(0) === d3_map_prefixCode) {
-          f.call(this, value.substring(1));
-        }
-      }
+      for (var value in this) if (value.charCodeAt(0) === d3_map_prefixCode) f.call(this, value.substring(1));
     }
   });
   d3.behavior = {};

src/arrays/map.js

@@ -38,12 +38,17 @@ d3_class(d3_Map, {
     this.forEach(function(key, value) { entries.push({key: key, value: value}); });
     return entries;
   },
+  size: function() {
+    var size = 0;
+    for (var key in this) if (key.charCodeAt(0) === d3_map_prefixCode) ++size;
+    return size;
+  },
+  empty: function() {
+    for (var key in this) if (key.charCodeAt(0) === d3_map_prefixCode) return false;
+    return true;
+  },
   forEach: function(f) {
-    for (var key in this) {
-      if (key.charCodeAt(0) === d3_map_prefixCode) {
-        f.call(this, key.substring(1), this[key]);
-      }
-    }
+    for (var key in this) if (key.charCodeAt(0) === d3_map_prefixCode) f.call(this, key.substring(1), this[key]);
   }
 });
 

src/arrays/set.js

@@ -28,11 +28,16 @@ d3_class(d3_Set, {
     });
     return values;
   },
+  size: function() {
+    var size = 0;
+    for (var value in this) if (value.charCodeAt(0) === d3_map_prefixCode) ++size;
+    return size;
+  },
+  empty: function() {
+    for (var value in this) if (value.charCodeAt(0) === d3_map_prefixCode) return false;
+    return true;
+  },
   forEach: function(f) {
-    for (var value in this) {
-      if (value.charCodeAt(0) === d3_map_prefixCode) {
-        f.call(this, value.substring(1));
-      }
-    }
+    for (var value in this) if (value.charCodeAt(0) === d3_map_prefixCode) f.call(this, value.substring(1));
   }
 });

test/arrays/map-test.js

@@ -51,6 +51,42 @@ suite.addBatch({
         assert.isFalse(b.has("bar"));
       }
     },
+    "size": {
+      "returns the number of distinct keys": function(map) {
+        var m = map();
+        assert.deepEqual(m.size(), 0);
+        m.set("foo", 1);
+        assert.deepEqual(m.size(), 1);
+        m.set("foo", 2);
+        assert.deepEqual(m.size(), 1);
+        m.set("bar", 2);
+        assert.deepEqual(m.size(), 2);
+        m.remove("foo");
+        assert.deepEqual(m.size(), 1);
+        m.remove("foo");
+        assert.deepEqual(m.size(), 1);
+        m.remove("bar");
+        assert.deepEqual(m.size(), 0);
+      }
+    },
+    "empty": {
+      "returns true only if the map is empty": function(map) {
+        var m = map();
+        assert.isTrue(m.empty());
+        m.set("foo", 1);
+        assert.isFalse(m.empty());
+        m.set("foo", 2);
+        assert.isFalse(m.empty());
+        m.set("bar", 2);
+        assert.isFalse(m.empty());
+        m.remove("foo");
+        assert.isFalse(m.empty());
+        m.remove("foo");
+        assert.isFalse(m.empty());
+        m.remove("bar");
+        assert.isTrue(m.empty());
+      }
+    },
     "forEach": {
       "empty maps have an empty keys array": function(map) {
         var m = map();

test/arrays/set-test.js

@@ -25,6 +25,42 @@ suite.addBatch({
         assert.isTrue(s.has("bar"));
       }
     },
+    "size": {
+      "returns the number of distinct values": function(set) {
+        var s = set();
+        assert.deepEqual(s.size(), 0);
+        s.add("foo");
+        assert.deepEqual(s.size(), 1);
+        s.add("foo");
+        assert.deepEqual(s.size(), 1);
+        s.add("bar");
+        assert.deepEqual(s.size(), 2);
+        s.remove("foo");
+        assert.deepEqual(s.size(), 1);
+        s.remove("foo");
+        assert.deepEqual(s.size(), 1);
+        s.remove("bar");
+        assert.deepEqual(s.size(), 0);
+      }
+    },
+    "empty": {
+      "returns true only if the set is empty": function(set) {
+        var s = set();
+        assert.isTrue(s.empty());
+        s.add("foo");
+        assert.isFalse(s.empty());
+        s.add("foo");
+        assert.isFalse(s.empty());
+        s.add("bar");
+        assert.isFalse(s.empty());
+        s.remove("foo");
+        assert.isFalse(s.empty());
+        s.remove("foo");
+        assert.isFalse(s.empty());
+        s.remove("bar");
+        assert.isTrue(s.empty());
+      }
+    },
     "forEach": {
       "empty sets have an empty values array": function(set) {
         var s = set();