#summary Explains the internal use of runtime functions in V8. = Introduction = Much of the !JavaScript library is implemented in JavaScript code itself, using a minimal set of C++ runtime functions callable from !JavaScript. Some of these are called using names that start with %, and using the flag "--allow-natives-syntax". Others are only called by code generated by the code generators, and are not visible in JS, even using the % syntax. = Details = Here are the V8 runtime functions, their JS names, if they are visible, and their documentation.