Capturing Data from an EventEmitter
EventEmitter is a very important class in Node.[11] It provides a channel for events to be dispatched and listeners notified. Many objects youâll encounter in Node inherit from EventEmitter, like the Streams we saw in the last section.
Now letâs modify our previous program to capture the child processâs output by listening for events on the stream. Open an editor to the watcher-spawn.js file from the previous section, then find the call to fs.watch(). Replace it with this:
| file-system/watcher-spawn-parse.js | |
| â | fs.watch(filename, âfunctionâ() { |
| â | âletâ |
| â | ls = spawn(â'ls'â, [â'-lh'â, filename]), |
| â | output = â''â; |
| â | ls.stdout.on(â'data'â, âfunctionâ(chunk){ |
| â | output ... |
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