load.js

Save the following to foo.js

a = "hello there,";
doStuff = function() {
    console.log("stuff is now being done");
}

Then the following script will read and execute this file inline:

load("foo.js");

console.log(a);
doStuff();

foo.js is loaded from the current working directory.

foo.js sets a and doStuff on the top level scope so the above script can access them after load('foo.js') is called.

The output is:

hello there,
stuff is now being done