class-based.js

// CommandHandler Class
var CommandHandler = function(repository) {
  this.handle = function(command) {
    // do stuff with repository and command
  }
}

// Elsewhere, create an instance of the class...
var myCommandHandler = new CommandHandler(repository);

// ...and use it
myCommandHandler.handle(command);

function-based.js

var _ = require('lodash'); // Lodash is an API-compatible fork of Underscore.js

// The same as the first example, but as a class-less function
var handle = function(repository, command) {
  // do stuff with repository and command
}

// Elsewhere, inject the repository by creating a partial
var handle = _.partial(handle, repository);

// ...and use it
handle(command);

partial-example.js

var sum = function(a, b) {
  return a + b;
}

var addFiveTo = partial(sum, 5);

sum(5, 10) // returns 15
addFiveTo(10) // returns 15