Arguments.callee

gistfile1.js

// this would not work since unnamed functions could not be passed and then called again inside of themselves
[1,2,3,4,5].map(function (n) {
    return !(n > 1) ? 1 : /* what goes here? */ (n - 1) * n;
});

// arguments.callee was added so you could do the following
[1,2,3,4,5].map(function (n) {
    return !(n > 1) ? 1 : arguments.callee(n - 1) * n;
});