diff --git a/README.md b/README.md
index 96b9b66..e626e48 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,7 @@ A lightweight JSON library for Lua
 
 
 ## Features
-* Implemented in pure Lua: works with 5.1, 5.2, 5.3 and JIT
+* Implemented in pure Lua: works with 5.1, 5.2, 5.3, 5.4 and JIT
 * Fast: generally outperforms other pure Lua JSON implementations
   ([benchmark scripts](bench/))
 * Tiny: around 280sloc, 9kb
diff --git a/json.lua b/json.lua
index 711ef78..372e69e 100644
--- a/json.lua
+++ b/json.lua
@@ -2,6 +2,7 @@
 -- json.lua
 --
 -- Copyright (c) 2020 rxi
+-- Copyright (c) 2020 alexandro-rezakhani
 --
 -- Permission is hereby granted, free of charge, to any person obtaining a copy of
 -- this software and associated documentation files (the "Software"), to deal in
@@ -22,7 +23,7 @@
 -- SOFTWARE.
 --
 
-local json = { _version = "0.1.2" }
+local json = { _version = "0.1.2fix" }
 
 -------------------------------------------------------------------------------
 -- Encode
@@ -64,22 +65,30 @@ local function encode_table(val, stack)
   if stack[val] then error("circular reference") end
 
   stack[val] = true
-
-  if rawget(val, 1) ~= nil or next(val) == nil then
-    -- Treat as array -- check keys are valid and it is not sparse
-    local n = 0
-    for k in pairs(val) do
-      if type(k) ~= "number" then
-        error("invalid table: mixed or invalid key types")
-      end
-      n = n + 1
-    end
-    if n ~= #val then
-      error("invalid table: sparse array")
-    end
+  -- Check whether to treat as a array or object
+  local array = true
+  local length = 0
+	local nLen = 0
+  for k,v in pairs(val) do
+		if (type(k) ~= "number" or k<=0) and not (k == "n" and type(v) == "number") then
+			array = nil
+			break	-- Treat as object
+		else
+			if k > length then 
+				length = k
+			end
+			if k == "n" and type(v) == "number" then
+				nLen = v
+			end
+		end
+  end
+  if array then
+		if nLen > length then
+			length = nLen
+		end
     -- Encode
-    for i, v in ipairs(val) do
-      table.insert(res, encode(v, stack))
+    for i=1,length do
+      table.insert(res, encode(val[i], stack))
     end
     stack[val] = nil
     return "[" .. table.concat(res, ",") .. "]"
@@ -87,10 +96,13 @@ local function encode_table(val, stack)
   else
     -- Treat as an object
     for k, v in pairs(val) do
-      if type(k) ~= "string" then
-        error("invalid table: mixed or invalid key types")
+      if type(k) == "string" then
+        res[#res + 1] = encode(k, stack) .. ":" .. encode(v, stack)
+      elseif type(k) == "number" then
+        res[#res + 1] = encode(string.format(k), stack) .. ":" .. encode(v, stack)
+      else
+        error("invalid table: mixed or invalid key types");
       end
-      table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))
     end
     stack[val] = nil
     return "{" .. table.concat(res, ",") .. "}"
@@ -108,7 +120,12 @@ local function encode_number(val)
   if val ~= val or val <= -math.huge or val >= math.huge then
     error("unexpected number value '" .. tostring(val) .. "'")
   end
-  return string.format("%.14g", val)
+  local intVal = math.tointeger(val)
+  if intVal == val then
+    return string.format("%d", intVal)
+  else
+    return string.format("%.14g", val)
+  end
 end