Carry forward NA values for multiple columns R - r

Question

I need to carry forward NA values from one column to the next. An example of the code is below
df <- data.frame(a = c(1,2,NA,NA,NA,NA,NA,NA,NA,NA),
b =c(NA,NA,3,4,NA,NA,NA,NA,NA,NA),
c = c(NA,NA,NA,NA,5,6,NA,NA,NA,NA),
d = c(NA,NA,NA,NA,NA,NA,7,8,NA,NA),
e = c(NA,NA,NA,NA,NA,NA,NA,NA,9,10))
I have tried to use a loop with the na.locf function in zoo but this only carries the previous columns values
columns <- seq(2,ncol(df))
output <- list()
for (i in columns){
output[[i]] <- t(zoo::na.locf(t(df[,(i-1):i])))[,2]
}
The expected output would be like
expected_output <- data.frame(a = c(1,2,NA,NA,NA,NA,NA,NA,NA,NA),
b = c(1,2,3,4,NA,NA,NA,NA,NA,NA),
c = c(1,2,3,4,5,6,NA,NA,NA,NA),
d = c(1,2,3,4,5,6,7,8,NA,NA),
e = c(1,2,3,4,5,6,7,8,9,10))

Answer 1

Transpose df, apply na.locf, transpose again and replace df contents with that to make it a data frame with the correct names.
library(zoo)
out <- replace(df, TRUE, t(na.locf(t(df), fill = NA)))
identical(out, expected_output)
## [1] TRUE
This also works and is similar except it applies na.locf0 to each row instead of applying na.locf to the transpose.
out <- replace(df, TRUE, t(apply(df, 1, na.locf0)))
identical(out, expected_output)
## [1] TRUE