Implementing waitFor functionality with phantomjs-node

Question

I have tried and tested - with success - the phantomjs example waitFor. However, I am having difficulty implementing it via the phantomjs-node module primarily because

Answer 1

I recently created a fairly simple node module to port waitFor over to node: https://gist.github.com/joseym/1d01edbcc40a7698f55a#file-phantomjs-waitfor-js

var async = require('async');

module.exports = waitFor;

/**
 * waitFor port used with 
 * @see    {@link https://github.com/ariya/phantomjs/blob/master/examples/waitfor.js}
 * @see    {@link https://github.com/sgentle/phantomjs-node}
 * @callback testFx - Test function, will repeat until true or timeout limit is reached
 * @callback onReady - Fires if/when `testFx` passes.
 * @param {(number|boolean|string)} [timeOut=false] - If defined and falsey or string value of`forever` 
 *                                                    then `waitFor` will run until `testFx` passes without 
 *                                                    timing out, otherwise pass a number in miliseconds.
 */
function waitFor(testFx, onReady, timeOut) {

    var maxtimeOutMillis = typeof timeOut !== 'undefined' ? timeOut : 5000 // Default Max Timout is 5s if not defined
        , start = new Date().getTime()
        , isAsync = testFx.length > 0
        , passing = undefined
    ;

    async.until(
        function Test() { 
            return typeof passing !== 'undefined'; 
        },
        function Action(cb) {
            setTimeout(function(){

                if (!maxtimeOutMillis || maxtimeOutMillis == 'forever' || new Date().getTime() - start < maxtimeOutMillis) {

                    // If a callback is passed to `testFx` we'll handle that.
                    function useCallback(){
                        passing = arguments[0]
                        return cb();
                    };                    

                    passing = (function(){
                        return (typeof(testFx) === "string" ? eval(testFx) : testFx).apply(this, arguments);
                    })(isAsync ? useCallback : undefined);

                    if(!isAsync) cb();

                } else {
                    return cb(new Error('`waitFor` timeout'));
                }

            }, 250);
        },
        function Done(err) {
            return (function(){
                return (typeof(onReady) === "string" ? eval(onReady) : onReady).apply(this, arguments);                  
            })(err, passing);
        }
    );

}