R method to convert a sentence into a friendly url.

friendlyUrl.R

#
# Converts text into a friendly url.
# Examples:
# friendlyUrl('She sells seashells by the seashore.') -> "she-sells-seashells-by-the-seashore"
# friendlyUrl('Learn To Program: 1,000 "Languages" in 2015.') -> "learn-to-program-1-000-languages-in-2015"
#
friendlyUrl <- function(text, sep = '-', max = 80) {
  # Replace non-alphanumeric characters.
  url <- gsub('[^A-Za-z0-9]', sep, text)
  
  # Remove double separators (do this twice, in case of 4 or 3 repeats).
  doubleSep <- paste(sep, sep, sep = '')
  url <- gsub(doubleSep, sep, url)
  url <- gsub(doubleSep, sep, url)
  
  # Convert to lowercase and trim to max length.
  url <- substr(tolower(url), 1, max)

  # Trim leading and trailing separators.
  gsub('^-+|-$', '', url)
}