After reading this answer i understand the benefits but am confused about the function

Question

I am looking to remove an item from a table using lua

a quick search led me to read that table.remove() is a bad idea due to efficiency

however i'm not 100% understanding the custom function

here is the function

function ArrayRemove(t, fnKeep)
local j, n = 1, #t;

for i=1,n do
    if (fnKeep(t, i, j)) then
        -- Move i's kept value to j's position, if it's not already there.
        if (i ~= j) then
            t[j] = t[i];
            t[i] = nil;
        end
        j = j + 1; -- Increment position of where we'll place the next kept value.
    else
        t[i] = nil;
    end
end

return t;
end

i understand the idea that we move the items and remove all in one loop rather than the table.remove() having to move everything ( there is a long answer here about it, Safely remove items from an array table while iterating)

looking at the function above, what would happen if the item to delete is the first item?

if we replace the line if (fnKeep(t, i, j)) then as suggested with (t[i] == 'deleteme')

then nothing happens as both i and j are 1

also if the first 'if' is false then the item is removed anyways?

can someone shed some light on this for me please

edit

I believe the working function would be as follows

local j, n = 1, #t -- t is table to iterate over

for i = 1, n do -- begin the loop

    if t[i] ~= 'object to delete' then -- if this is NOT the item to remove 

        if i ~= j then -- can it be moved to new position

            t[j] = t[i] -- move to new pos
            t[i] = nil -- clear old pos

        end

        j = j + 1 -- increment the new pos counter

        end

    else -- if it is the item TO delete then delete it

    t[i] = nil

end