feature: added new cjson.array_mt metatable to allow enforcing JSON array encoding.

Signed-off-by: Yichun Zhang (agentzh) <agentzh@gmail.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/README.md b/README.md
index 7282a4d..1cdb53b 100644
--- a/README.md
+++ b/README.md
@@ -11,6 +11,7 @@ Table of Contents
 * [Additions to mpx/lua](#additions)
     * [encode_empty_table_as_object](#encode_empty_table_as_object)
     * [empty_array](#empty_array)
+    * [array_mt](#array_mt)
     * [empty_array_mt](#empty_array_mt)
     * [encode_number_precision](#encode_number_precision)
 
@@ -76,6 +77,39 @@ This will generate:
 
 [Back to TOC](#table-of-contents)
 
+array_mt
+--------
+**syntax:** `setmetatable({}, cjson.array_mt)`
+
+When lua-cjson encodes a table with this metatable, it will systematically
+encode it as a JSON Array. The resulting, encoded Array will contain the array
+part of the table, and will be of the same length as the `#` operator on that
+table. Holes in the table will be encoded with the `null` JSON value.
+
+Example:
+
+```lua
+local t = { "hello", "world" }
+setmetatable(t, cjson.array_mt)
+cjson.encode(t) -- ["hello","world"]
+```
+
+Or:
+
+```lua
+local t = {}
+t[1] = "one"
+t[2] = "two"
+t[4] = "three"
+t.foo = "bar"
+setmetatable(t, cjson.array_mt)
+cjson.encode(t) -- ["one","two",null,"three"]
+```
+
+This value was introduced in the `2.1.0.5` release of this module.
+
+[Back to TOC](#table-of-contents)
+
 empty_array_mt
 --------------
 **syntax:** `setmetatable({}, cjson.empty_array_mt)`