You can quickly join a series of lines onto a single line using the J
command. Simply hitting 'J' in normal mode will join the current line with
the line below it leaving a space in between the two. If you want to join
the next 5 lines, you can hit 5J. Hitting '5J' on this:
first,
second,
third,
fourth,
fifth
will transform it into this:
first, second, third, fourth, fifth
Similarly, you can perform a line by line join on a visual selection by
hitting J after making the desired visual selection.