I use this for Jake dependencies that only need to run once.

once.js

/**
 * makes sure a function is only executed once
 * all future runs of the function return the same result instantly
 * I use this for Jakefiles where tasks should not run twice as dependencies
 *
 * by @jonashuckestein
 */
var once = function(fn) {
    var self = this;
    var ran_once = false;
    var result = undefined;
    return function() {
        if (ran_once == false) {
            result = fn.apply(self, arguments);
            ran_once = true;
        }
        return result;
    };   
};