coalesce.(...)

# Use a single value to replace all missing values
x <- sample(c(1:5, NA, NA, NA))
coalesce.(x, 0)

# Or match together a complete vector from missing pieces
y <- c(1, 2, NA, NA, 5)
z <- c(NA, NA, 3, 4, 5)
coalesce.(y, z)

# Supply lists with dynamic dots
vecs <- list(
  c(1, 2, NA, NA, 5),
  c(NA, NA, 3, 4, 5)
)
coalesce.(!!!vecs)