efficient is.na tabulation?

I am aware of

table(is.na(df$var))

but is there an efficient way of create a table that shows the number of
missing values in each variable of a data frame?

Right now I am forced to create a new variable, varna<-is.na(df$var), for
each variable of the data frame, bind them to a new data frame and tabulate
it, but surely there is a simpler way?

any help is greatly appreciated,
angelo

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