Custom backbone.js Collection.fetch() that doesn't execute if the last instance hasn't completed yet.

backbone_collection_fetch.js

// Override the default Backbone.collection.fetch()
// to avoid being called before the last one has finished
Backbone.Collection.prototype.fetch = _.wrap(
  Backbone.Collection.prototype.fetch,
  function(original_fetch) {
    var args = Array.prototype.slice.call(arguments, 1);

    // Check if the last fetch() is still underway, if so skip this one.
    if (this.fetch_pending === true) return;
    
    this.fetch_pending = true;
    try {
      return original_fetch.apply(this, args).always(function() { self.fetch_pending = false; });
    } catch(err) {
      this.fetch_pending = false;
    }
  }
);