WebAssembly only uses the same web APIs as javascript, has generally been implemented using code already used for supporting javascript, and was designed from t

WebAssembly only uses the same web APIs as javascript, has generally been implemented using code already used for supporting javascript, and was designed from the ground up for this use inside the web sandbox, as opposed to Java which was designed in the same way as most language runtimes based around unsandboxed access to a system and then had a security layer grafted onto it.