Need a proceed of clumping columns together but trailing NAs and reversing a result

I am looking for a proceed of formulating a new buttress stoical of a set
columns (bin 1-9 in this example) from an existent information support but
trailing NAs and a law reversed. All this but controlling loops. Thanks
for your help!data set example:id bin_1 bin_2 bin_3 bin_4 bin_5 bin_6
bin_7 bin_8 bin_91 a b c d e na na na na2
a b na na na na na na naideal result:id
reversed_noNAs1 edcba2 baI customarily brew fields controlling
do.call/paste though this clumps in a NAs:do.call(paste, c(df[c("bin_1",
"bin_2", "bin_3", "bin_4", "bin_5", "bin_6","bin_7","bin_8","bin_9")], sep
= ""))thanks!