Using a for loop as an argument in an if statement in R

I have a list of categories and I can get the number of apps for each category in this list. I'd like to find the 10 categories that have the most apps. I wrote this code which does not work right now, I'm getting this error:

 Error in if (for (topCategoryNb in top10Nb) { : 
  argument is of length zero

So I'm assuming this is because a for loop cannot be put as an argument in an if statement. Is there a better way to do what I'm trying to do? If not how can I fix my code?

Here is the code:

top10 <- list()
top10Nb <- list()
for(category in allCategories){
  currentNb<- numberAppPerCategories(category,0)
  print(category)
  print(currentNb)
  if(
    for(topCategoryNb in top10Nb){topCategoryNb<currentNb}
  ){
    top10 <- c(top10, category)
  }
  allCategories[- category]  
}