The Foundation core library is available in SwiftWasm, but in a limited capacity. The main reason is that the Dispatch core library is unavailable due to the lack of standardized multi-threading support in WebAssembly and SwiftWasm itself. Many Foundation APIs rely on the presence of Dispatch under the hood, specifically file system access and threading helpers. A few other types are unavailable in browsers or aren't standardized in WASI hosts, such as support for sockets and low-level networking, or support for time zone files, and they had to be disabled. These types are therefore absent in SwiftWasm Foundation:
Related functions and properties on other types are also absent or disabled. We would like to make them available in the future as soon as possible, and we invite you to contribute and help us in achieving this goal!