less obscure Ox.map

source/Ox/js/Collection.js

@@ -111,6 +111,7 @@ Ox.filter <f> Filters a collection by a given condition
 @*/
 Ox.filter = function(col, fn, that) {
     var ret, type = Ox.typeOf(col);
+    fn = fn || Ox.identity;
     if (type == 'object') {
         ret = {};
         Ox.forEach(col, function(val, key) {
@@ -303,6 +304,16 @@ Ox.indexOf = function(col, fn) {
     return index == col.length ? -1 : index;
 };
 
+// FIXME: use this instead of `Ox.filter(Ox.map())` when it's just about getting
+// the original indices
+Ox.indicesOf = function(col, fn) {
+    return Ox.map(col, function(val, i) {
+        return fn(val) ? i : null;
+    }).filter(function(index) {
+        return index !== null;
+    });
+};
+
 /*@
 Ox.isEmpty <f> Tests if a value is an empty array, object or string
     (value) -> <b> True if the value is an empty array, object or string
@@ -460,8 +471,7 @@ Ox.makeObject = function(arr) {
 /*@
 Ox.map <f> Transforms the values of an array, object or string
     Unlike <code>[].map()</code>, <code>Ox.map()</code> works for arrays,
-    objects and strings. Returning <code>null</code> from the iterator
-    function will remove the element from the collection.
+    objects and strings.
     > Ox.map([0, 0, 0], function(v, i) { return v == i; })
     [true, false, false]
     > Ox.map({a: 'a', b: 'a', c: 'a'}, function(v, k) { return v == k; })
@@ -474,21 +484,19 @@ Ox.map <f> Transforms the values of an array, object or string
     # > Ox.map([,], function(v, i) { return i; })
     # [0]
 @*/
-
-// FIXME: it would sometimes be nice to have Ox.map(3, function(i) {...})
-// instead of Ox.range(3).map(function(i) {...})
-
-Ox.map = function(obj, fn) {
-    // fixme: return null to filter out may be a bit esoteric
-    var isObject = Ox.isObject(obj),
-        ret = isObject ? {} : [];
-    Ox.forEach(obj, function(val, key) {
-        // FIXME: is there any reason for this strange assignment?
-        var map;
-        if ((map = fn(val, key)) !== null) {
-            ret[isObject ? key : ret.length] = map;
+Ox.map = function(col, fn, that) {
+    var type = Ox.typeOf(col), ret;
+    if (type == 'object') {
+        ret = {};
+        Ox.forEach(col, function(val, key) {
+            ret[key] = fn.call(that, val, key, col);
+        });
+    } else {
+        ret = Ox.toArray(col).map(fn);
+        if (type == 'string') {
+            ret = ret.join('');
         }
-    });
+    }
     return ret;
 };