Logging in Grunt, in colour

Grunt provides various functions for logging, such as grunt.log.error() and grunt.log.ok(). Most of these prepend the message with ‘>>’ and don’t colour the message itself.

If you just want to output a coloured string, use grunt.log.write() or grunt.log.writeln() together with the colours provided by the colors library. Here is an example:

grunt.registerTask('all-done', function() {
    grunt.log.writeln('Congratulations! You have finished ' + '42'.green + ' tasks.');

The colors library (which can also change other font properties, by the way) achieve its magic by extending the String prototype. The actual colouring is achieved by adding some control characters, as can be seen from the following code snippet.

  if (exports.mode === 'console') {
    styles = {
      'bold'      : ['\x1B[1m',  '\x1B[22m'],
      'italic'    : ['\x1B[3m',  '\x1B[23m'],
      'underline' : ['\x1B[4m',  '\x1B[24m'],
      'inverse'   : ['\x1B[7m',  '\x1B[27m'],
      'strikethrough' : ['\x1B[9m',  '\x1B[29m'],
      //text colors
      'white'     : ['\x1B[37m', '\x1B[39m'],
      'grey'      : ['\x1B[90m', '\x1B[39m'],
      'black'     : ['\x1B[30m', '\x1B[39m'],
      'blue'      : ['\x1B[34m', '\x1B[39m'],
      'cyan'      : ['\x1B[36m', '\x1B[39m'],
      'green'     : ['\x1B[32m', '\x1B[39m'],
      'magenta'   : ['\x1B[35m', '\x1B[39m'],
      'red'       : ['\x1B[31m', '\x1B[39m'],
      'yellow'    : ['\x1B[33m', '\x1B[39m'],
      //background colors
      'whiteBG'     : ['\x1B[47m', '\x1B[49m'],
      'greyBG'      : ['\x1B[49;5;8m', '\x1B[49m'],
      'blackBG'     : ['\x1B[40m', '\x1B[49m'],
      'blueBG'      : ['\x1B[44m', '\x1B[49m'],
      'cyanBG'      : ['\x1B[46m', '\x1B[49m'],
      'greenBG'     : ['\x1B[42m', '\x1B[49m'],
      'magentaBG'   : ['\x1B[45m', '\x1B[49m'],
      'redBG'       : ['\x1B[41m', '\x1B[49m'],
      'yellowBG'    : ['\x1B[43m', '\x1B[49m']

For example, you could use

console.log('This is a \x1B[1m\x1B[31mBOLD\x1B[39m\x1B[22m proposal!');

to have the word BOLD output in bold and red.