The cache object mentioned in the descriptions of elinks.load_uri and elinks.preformat_html is a wrapper for the internal ELinks cache object. ELinks passes the ECMAScript cache object as an argument to your ECMAScript function, and keeps the corresponding document in the cache until the function returns. After that, ELinks may remove the document from the cache, even if the function has saved the cache object to some global variable. Such an expired cache object does not work but it does not crash ELinks either.
Compatibility: ELinks 0.11.0