Embodiments relate to an isolated program execution environment. An aspect includes receiving, by the isolated program execution environment on a computer comprising a processor and a memory, a request to run a program. Another aspect includes wrapping program code corresponding to the program as a function. Another aspect includes cloning a real global object of the isolated program execution environment to create a fake global object. Another aspect includes passing the fake global object to the function. Another aspect includes executing the function, such that the function executes the program.