meta_tags.js

// ...

  render: function() {
    this.setMetaTags();
    // ...
  },


  setMetaTags: function() {
    var self, title, url, tags;
    self  = this;
    title = {'metaName': 'property', 'name': 'og:title', 'value': this.model.get('location_from') + ' to ' + this.model.get('location_to')}
    url = {'metaName': 'property', 'name': 'og:url', 'value': app_uri + '/#posts/' + this.model.get('id')}
    tags = [title, url];
    
    _.each(tags, function(item) {
      self.setOrCreateMetaTag(item.metaName, item.name, item.value);
    });
  },

  setOrCreateMetaTag: function(metaName, name, value) {
    var t = 'meta['+metaName+'="'+name+'"]';
    var mt = $(t);
    if (mt.length === 0) {
      t = '<meta '+metaName+'="'+name+'" />';
      mt = $(t).appendTo('head');
    }
    mt.attr('content', value);

    return mt;
  }

// ...