grunt-replace.js

options: {
    patterns: [
        {
            src: ['assets/js/**/*.js', 'assets/css/**/*.css',],
            search: /@@([^@]+?)@@/g,
            replace: function(matched, part, offset, string) {
                if(summary[part]) {
                    return summary[part];
                }
                else {
                    return part;
                }
            }
        }
    ]
}

test.js

var summary = {
  '/js/custom/index.js' : '/js/custom/index.a67bcd.js',
  '/js/custom/facilitySearch.js' : '/js/custom/facilitySearch.k89han.js',
  '/img/foo/bar/eversport.png' : '/img/foo/bar/eversport.9iasdui.png',
};
var search = /@@([^@]+?)@@/g;

var htmlString = `
 block append scripts
   script(src="@@/js/custom/index.js@@")
<script src="@@/js/custom/boostrap.js@@"></script>
<p>
<h1>Hallo Welt</h1>
</p>
<script src="@@/js/custom/facilitySearch.js@@"></script>
`;

var cssString = `
body {
  background-image: url('@@/img/foo/bar/eversport.png@@');
}
`;

var replace = function(matched, part, offset, string) {
    if(summary[part]) {
        return summary[part];
    }
    else {
        return part;
    }
};

htmlString.replace(search, replace);
cssString.replace(search, replace);