How to configure this library to not to delete the files in output folder?

[aravinth-r-7867]

const treeSync = require('tree-sync');
const dir1 = '/Users/test/Documents/Repositories/svg-bucket/tests/dummy/svg/svg-bucket/test2';
const dir2 = '/Users/test/Documents/Repositories/svg-bucket/tests/dummy/svg/svg-bucket/test1';
const tree = new treeSync(dir1, dir2);
tree.sync();

This is how I tried this library. I want to preserve the files in the dir2 folder. I just want to move the files from dir1 to dir2. Is there way to preserve files in dir2 or is there any other plugin to do this??
Thanks in advance.