grunt task for compiling CoffeScript

grunt-coffee.js

/*
 * Grunt Task File
 * ---------------
 *
 * Task: coffee
 * Description: Compile CoffeeScript files
 * Dependencies: coffee-script
 *
 */

module.exports = function(grunt) {

  var log = grunt.log,
      file = grunt.file,
      _ = grunt.utils._,
      path = require('path'),
      fs = require('fs');

  grunt.registerMultiTask('coffee', 'Compile CoffeeScript files', function() {

    var files = file.match(this.file.src, file.watchFiles.changed),
        dest = this.file.dest,
        base = this.file.src.match(/^[^\*]*/)[0],
        tmpFilePath;

    // Delete any compiled files matching a pontentially deleted source coffee files
    if (file.watchFiles.deleted) {
      file.match(this.file.src, file.watchFiles.deleted).forEach(function(filepath) {
        var tmpFilePath = path.join(dest, (filepath.replace(/\.coffee$/, '.js')).substr(base.length));
        if(path.existsSync(tmpFilePath)) {
          fs.unlinkSync(tmpFilePath);
          log.ok('File "' + tmpFilePath + '" deleted.');
        }
      });
    };

    // If the task is called directly and not through a watch task
    if (file.watchFiles.changed === null && file.watchFiles.deleted === null) {
      log.writeln('Compiling all matching coffee files');
      files = file.expand(this.file.src);
    }

    // Compile all the files and save them at the defined destination
    files.forEach(function(filepath) {
      var js,
          tmpFilePath = path.join(dest, (filepath.replace(/\.coffee$/, '.js')).substr(base.length));
      if(!path.existsSync(path.dirname(tmpFilePath))) {
        file.mkdir(path.dirname(tmpFilePath));
      }
      js = grunt.helper('coffee', filepath);
      if(js.length) {
        file.write(tmpFilePath, js);
        log.ok('File "' + filepath + '" compiled to "' + tmpFilePath + '".');
      }
    });

    // Fail task if errors were logged.
    if (grunt.errors) { return false; }

  });

  grunt.registerHelper('coffee', function(filepath) {
    
    var coffee = require('coffee-script'),
        js = '';

    try {
      js = coffee.compile(grunt.file.read(filepath), { bare: true });  
    } catch(e) {
      log.error(e);
    }

    return js;

  });

};

Where should I put this file?

It is a grunt task. Here's where you can start with it:

https://github.com/cowboy/grunt/blob/master/docs/getting_started.md

The short version to the answer is you can put it in the tasks folder of your project or in ~/.grunt/tasks if you want to use it on different projects.

yeah I tried to put it in ~/.grunt/tasks and it works, thanks

If I want to put coffee file and compiled js file at same place, this grunt task seem failed.

coffee:
  dev: 
    src: './**/*.coffee',
    dest: './'
watch:
  files: '<config:coffee.dev.src>',
  tasks: 'coffee:dev'