module.js

Module = {};

(function () {
  var modules = {};
  var queue   = [];
  var alias   = {};

  function queueCallback()
  {
    for (var i in queue) {
      var j = 0;
      for (j = 0; j < queue[i].depend.length; j++) {
        if (!modules[queue[i].depend[j]])
          break;
      }

      if (j < queue[i].depend.length)
        continue;

      queue[i].callback();
      delete queue[i];
    }

    var newq = [];
    for (var i in queue) {
      if (queue[i])
        newq.push(queue[i])
    }

    queue = newq;
  }

  function scriptLoaded(js)
  {
    return function () {
      modules[js] = true;
      queueCallback();
    };
  }

  Module.call = function (callback, jss) {
    var dep = [];
    for (var i in jss) {
      var js = jss[i];
      if (alias[js])
        js = alias[js];

      if (modules[js])
        continue;
      dep.push(js);
    }

    if (dep.length == 0) {
      callback();
      return;
    }

    queue.push({callback: callback, depend: dep});

    $.ajaxSetup({cache: true});
    for (var i in dep) {
      if (modules[dep[i]] !== undefined)
        continue;

      modules[dep[i]] = false; // 标记一下

      $.getScript(dep[i], scriptLoaded(dep[i]));
    }
    $.ajaxSetup({cache: false});
  };

  Module.preLoad = function (jss) {
    $.ajaxSetup({cache: true});
    for (var i in jss) {
      var js = jss[i];
      if (alias[js])
        js = alias[js];

      if (modules[js] === undefined )
        $.getScript(js, scriptLoaded(js));
    }
    $.ajaxSetup({cache: false});
  };

  Module.init = function ()
  {
    $('script').each(function (i, item) {
      var src = $(item).attr('src');
      if (src != '')
        modules[src] = true;
    });
  };

  Module.alias = function (jss) {
    $.extend(alias, jss);
  };
})();

$(Module.init);