For my own script I imported multiple tiff-sequences with this:
var path = "~insert your filepath here ~";
var io = new ImportOptions(File(path));
if (io.canImportAs(ImportAsType.FOOTAGE));
io.importAs = ImportAsType.FOOTAGE;
// if your footage is an image-sequence:
io.sequence = true;
io.forceAlphabetical = true;
tiffseq = app.project.importFile(io);
tiffseq.name = 'My automatically imported foorage";
theComp = app.project.activeItem; //currently selected composition(example)
theComp.layers.add(tiffseq);
Hope it helps!
Layout/compositor for Animation show.