.has with tests

lib/hash.js

@@ -61,6 +61,11 @@ function Hash (hash, xs) {
         merge : function (h) {
             return self.copy.update(h);
         },
+        has : function (key) { // only operates on enumerables
+            return Array.isArray(key)
+                ? key.every(function (k) { return self.has(k) })
+                : self.keys.indexOf(key.toString()) >= 0;
+        },
         valuesAt : function (keys) {
             return Array.isArray(keys)
                 ? keys.map(function (key) { return hash[key] })
@@ -153,6 +158,10 @@ Hash.merge = function (a, b) {
     return Hash(a).merge(b).items;
 };
 
+Hash.has = function (ref, key) {
+    return Hash(ref).has(key);
+};
+
 Hash.valuesAt = function (ref, keys) {
     return Hash(ref).valuesAt(keys);
 };

test/hash.js

@@ -143,3 +143,18 @@ exports.zip = function (assert) {
     assert.equal(zipped.b, 2);
     assert.equal(zipped.c, 3);
 };
+
+exports.has = function (assert) {
+    var h = { a : 4, b : 5 };
+    var hh = Hash(h);
+
+    assert.ok(hh.has('a'));
+    assert.equal(hh.has('c'), false);
+    assert.ok(hh.has(['a','b']));
+    assert.equal(hh.has(['a','b','c']), false);
+
+    assert.ok(Hash.has(h, 'a'));
+    assert.equal(Hash.has(h, 'c'), false);
+    assert.ok(Hash.has(h, ['a','b']));
+    assert.equal(Hash.has(h, ['a','b','c']), false);
+};