Process a series of JavaScript functions in the order supplied.

waterfall.js

/**
 * Process a set of functions in order supplied.
 *
 * @author Amir Khawaja <[email protected]>
 * @param {array} funcs - An array of functions
 */
function waterfall(funcs, done) {
    if (funcs !== void 0 && funcs !== null) {
        if (typeof funcs !== 'object' && funcs.shift !== void 0) {
            throw new Error('Array of functions expected');
        } else {
            if (funcs.length === 0) {
                throw new Error('Empty function array detected');
            }
        }
    }

    var lastReturnValue = null;
    var runner = null;
    var callback = function (err, results) {
        if (err !== void 0 && err !== null) {
            console.error(err);
        }

        lastReturnValue = results;
        runner();
    };
    var dispatcher = function (fn, handler) {
        try {
            runner = handler;
            window.setTimeout(fn.bind(null, lastReturnValue, callback), 0);
        } catch (e) {
            console.error(e);
        }
    };
    (function run() {
        if (funcs.length !== 0) {
            dispatcher(funcs.shift(), run);
        } else {
            done && done(lastReturnValue);
        }
    })();
}