不确定我是否理解这个问题，但我不认为Firebug对待任何外部JavaScript与内部不同。只需转到脚本选项卡，在下拉列表中选择.js文件并设置断点。

Not sure if I understand the question, but I don't think Firebug treats external javascript any differently than internal one. Just go to the "script" tab, select the .js file in the drop down list and set your breakpoint.