log

This may not be everyone's cup o' tea, but this is the library I've written for console.log-style debugging.

Improvements over console.log

• Timestamps (with optional timezone configuration)
• Filename and line number of the caller
  • CoffeeScript files have correct line numbers too (using coffee-errors)
• Colored log levels (using chalk)
• Objects and arrays are pretty-printed using JSON.stringify instead of [object Object]
• Error objects are pretty printed (using pretty-error)
  • Long stack traces included (using the stack-trace and clarify)
• Smart truncation of long strings and arrays
• 'quiet' option to quickly turn logging off/on
• 'filename' option to write directly to a file instead of stdout
• EventEmitter interface so you can listen for log messages (say, to copy all messages to the Captain's log, or perform evasive manuvers on 'error' and 'fatal' messages)

Usage

// A single, global log object. Don't call with "new".
log = require('log')

// Calling setup is optional.
log.setup({
  filename: String   // optional, if specified writes to file instead of stdout (has precedence over `stdout`)
  quiet: Bool        // optional, default false, if true turns disables output but still triggers events
  timezone: String   // optional, defaults to "America/New_York"
  colors: Bool       // optional, default is chalk's autodetect behavior
  stdout: Stream     // optional, if specified log writes to a Writable Stream instead of process.stdout (since v1.1.0)
  cutoffLength: Number // optional, default 250, the length to truncate long strings (since v1.1.0)
})

// Available log methods
log.log(args...)
log.debug(args...)
log.info(args...)
log.warn(args...)
log.err(args...)
log.fatal(args...)

// Event listener example(s)
log.on('err', function(e) {
  // Print errors to stderr
  process.stderr.write('ERROR: ' + e.message)
})
log.once('fatal', function(e) {
  // Take 'fatal' errors literally
  process.exit(1)
})

Example output

Screenshot of the colorized log levels, using Solarized terminal color scheme:

Example of a pretty error stack: