nova

Prioritizes memory footprint over speed; the README admits performance is acceptable but not fast and is not a high priority, making it unsuitable for compute-intensive tasks.

Lacks key ECMAScript features like RegExp lookaheads/lookbehinds and Promise subclassing, with the README noting non-compliance in regex implementation.

Array implementation does not support sparse storage, so creating large arrays allocates memory for all elements, wasting resources in edge cases.

Cannot execute WebAssembly, limiting use in environments that require both JavaScript and WASM, as explicitly stated in the shortcomings.