1. a.js
    2. b.js
    3. c.js

1. a.min.js
    2. b.min.js
    3. c.min.js

min: {
    dist: {
    src:  'js/**/*.js',
    dest: 'js/min/xxx.min.js'
   }
 }

uglify: {
      build: {
        files: [{
            expand: true,
            src: '**/*.js',
            dest: 'build/scripts',
            cwd: 'app/scripts'
        }]
      }
    }

uglify: {
    dist: {
        files: {
            'dist/main.js': 'src/main.js',
            'dist/widget.js': 'src/widget.js'
        }
    }
}

min: {
    files: grunt.file.expandMapping(['path/*.js', 'path2/*.js'], 'destination/', {
        rename: function(destBase, destPath) {
            return destBase+destPath.replace('.js', '.min.js');
        }
    })
}

min: {
    min_a: {
       src:  'a.js',
       dest: 'a.min.js'
    },
    min_b: {
       src:  'b.js',
       dest: 'b.min.js'
    },
    min_c: {
       src:  'c.js',
       dest: 'c.min.js'
 }

module.exports = function(grunt) {

  // Project configuration.
  grunt.initConfig({
    pkg: grunt.file.readJSON('package.json'),
    uglify: {
    build: {
        files: [{
            expand: true,
            src: '**/*.js',
            dest: 'build/scripts',
            cwd: 'public_html/app',
        ext: '.min.js'
        }]
      }
    }
  });

  // Load the plugin that provides the "uglify" task.
  grunt.loadNpmTasks('grunt-contrib-uglify');

  // Default task(s).
  grunt.registerTask('default', ['uglify']);

};

copy: {
  dist: {
    src: 'a.js',
    dest: 'a.min.js'
  }
},
minidirect: {
  all: 'js/min/*.min.js'
}

var filesA = 'a.js', filesB = 'b.js', filesC = 'c.js';

  ...

  min: {
      min_a: {
         src:  filesA,
         dest: 'a.min.js'
      },
      min_b: {
         src:  filesB,
         dest: 'b.min.js'
      },
      min_c: {
         src:  filesC,
         dest: 'c.min.js'
  }

  watch: {
      min_a: {
         files:  filesA,
         tasks: ['min:min_a']
      },
      min_b: {
         files:  filesB,
         tasks: ['min:min_b']
      },
      min_c: {
         files:  filesC,
         tasks: ['min:min_c']
      }
  }

uglify: {
  dist: {
    files: [{
      expand: true,
      src: '**/*.js',
      dest: 'destdir',
      cwd: 'srcdir',
      rename: function(dest, src) { return dest + '/' + src.replace('.js', '.min.js'); }
    }]
  }
},