MyPackage.aggregateAsset(‘js’,‘first.js’,{global:true, weight: -4, group: ‘header’});

The line that gets loaded in your head.html calls the header group and injects the js you want to include first- in packages/system/server/views/includes/head.html

<script type="text/javascript" src="/modules/aggregated.js?group=header"></script>

这个设置的说明怎么理解？求高手