thunk.js

function lazy(f) {
    return function () {
        var self = this, args = arguments;

        return function () {
            var data = f.apply(self, args);
            return typeof data === "function" ?
                data.apply(this, arguments) : data;
        };
    };
}

function evaluate(thunk) {
    return typeof thunk === "function" ? thunk() : thunk;
}

function add(a) {
    return function(b) {
        return a + b;
    };
}