/// `makePlus1` doesn't return an argument, but returns
/// a function that does.  `makePlusN` takes one argument,
/// and returns a function that itself takes an argument.
function makePlus1() {
    return function(x) { return x + 1; }
}
log(makePlus1()(10));function makePlusN(n) {
    return function(x) { return x + n; }
}
var plus10 = makePlusN(10);
log(plus10(100));