添加了Javascript属性，但不可见

Question

所以我试图将一个属性添加到一个包含对象名称的对象。这将在html名称属性等中使用。

setClientSideOpeningHours: =>
    newOpeningHours = {}
    existingOpeningHours = _.extend {}, @.get("opening_hours")
     _.each _.keys(existingOpeningHours), (item) ->
        newOpeningHours[item] = existingOpeningHours[item]
        newOpeningHours[item]["day"] = item
    console.log "openingHours.friday", newOpeningHours.friday,
                "openingHours.friday.day", newOpeningHours.friday.day
    @.set "clientside_opening_hours", newOpeningHours

在Chrome中，这会打印到控制台：

  

openingHours.friday   openingHours.friday：Object {is_closed：“true”， proto ：Object}   openingHours.friday.day：周五

稍后，在模型之外，当我调用@ .model.toJSON（）或@ .model.attributes时，day属性完全不存在。这是怎么回事？

编辑：使用$ .extend（true，...）

setClientSideOpeningHours: =>
    newOpeningHours = {}
    existingOpeningHours = $.extend true, {}, @.get("opening_hours")
    _.each .keys(existingOpeningHourshours), (item) =>
        newOpeningHours[item] = $.extend true, {}, existingOpeningHours[item]
        newOpeningHours[item].day = item
    @.set "clientside_opening_hours", newOpeningHours