Node.js lodash mixin()

var _ = require('lodash');

// use _.mixin to extend the lodash api

_.mixin({average: function(collection, callback) {

  return _(collection)
      .map(callback) /*from ww  w.j a v  a2  s  . com*/
      .reduce(function(result, item) {
        return result + item;
      }) / _.size(collection);
}});


var scores = [ 4, 5, 4, 4, 5, 5, 3];
var avgScore = _.average(scores).toFixed(2);

console.log(avgScore);