Mastering JavaScript Design Patterns

Filters and pipes

If you're at all familiar with the Unix command line, or to a lesser extent, the Windows command line, then you'll have probably made use of pipes. A pipe, which is represented by the | character, is short hand for "take the output of program A and put it into program B." This relatively simple idea makes the Unix command line incredibly powerful. For instance, if you wanted to list all the files in a directory and then sort them and filter for any files that start with either the letter b or g and end with an f, then the command might look like this:

ls|sort|grep "^[gb].*f$"

The ls command lists all files and directories, the sort command sorts them, and the grep command matches filenames against a regular expression. Running ...