simple javascript methods such as pop(),splice(),indexOf(),instanceof(),extend(),apply() in lua

Js-->Lua

function pop (arr)
      local d = arr[table.getn(arr)]
      table.remove(arr)
      return d   
end

function instanceof (obj1,obj2)
      obj2 = tostring (obj2)
      local mt = getmetatable (obj1)
 
      while true do
       	    if mt == nil then return false end
       	    if tostring (mt) == super then return true end
 	    mt = getmetatable (mt)
      end  
end

function indexOf (arr, elem)
      local result
      if "table" == type(arr) then
      	 for i=1,#arr do
	     if elem = arr[i] then
	     	result = i
		break
             end
          end
      end
      return result
end

function splice (arr, index, howmany)
      local new_arr = {}
      local table_size = table.getn(arr)

      if index < 1 then
      	 index = 1
      end

      if howmany < 0 then
      	 howmany = 0
      end

      if index > table_size then
      	 index = table_size + 1
	 howmany = 0
      end

      if index + howmany > table_size then
      	 howmany = table_size - index + 1
      end

      for i=1,index do
      	  table.insert(new_arr,arr[i])
      end

      for i=index + howmany - 1,table_size do
      	  table.insert(new_arr,arr[i])
      end

      return new_arr
end

function extend (parent, obj1, obj2)
      if type(obj2) ~= "table" then
      	 return
      end

      for i,v in pairs(obj2) do
      	  table.insert(obj1,i,v)
      end

      if type(parent) ~= "table" then
      	 return obj1 or parent 
      end
      temp_obj = obj1 or {}
      temp_obj.__index = parent
      return setmetatable(parent, temp_obj)
end

function apply (cb, self, obj)
      if type(cb) == "function" then
      	 cb = Object:extend()
      	 setmetatable(cb:new(),{__index = self})
	 cb(obj)
      end 
end