setTimeout in nodejs

Question

I've been trying to figure out how to use the timeout, problem with my code is that its way to fast, I could not discover how to do it with Request. everything else seems to work great

var Scraper = function() {
    for (i in userid) {


        //create complete url 
        totalurl = facebookurl + userid[i];

        // request facebook open graph

// WARNING the request func should be called every 1-3 secs? 

       request(totalurl, function(error, response, html) {
            if (!error && response.statusCode == 200) {

                // console.log(html);




            }
        });

    };
};


    Scraper();

Try replacing the for loop with a setInterval with a time of 3000 and increment the index manually — maksion
– maksion, Commented Nov 12, 2014 at 10:52
Nope, I think the best way for your application would be to use EventEmitter and raise an event when request is done. That way you'll be sure when another request is sent, the previous one is finished. — T00rk
– T00rk, Commented Nov 12, 2014 at 10:54

Geert-Jan · Accepted Answer · 2014-11-12 14:34:22Z

2

This is the gist of it using recursion:

    var userids = [//ids here];

    function processNextUrl(index){
        var userid = userids[index];
        totalurl = facebookurl + userid[index];
        request(totalurl, function(error, response, html) {
            if (!error && response.statusCode == 200) {
                //process
            }
            if(userids.length > index -1){ //stuff left to do
                setTimeout(function(){
                    processNextUrl(index+1);
                }, 3000);
            }
        });
    }

    processNextUrl(0); //kickstart the lot

edited Nov 12, 2014 at 14:34

answered Nov 12, 2014 at 11:11

Geert-Jan

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3 Comments

Klaaz0r Over a year ago

For some reason I get that "i is not defined"

Geert-Jan Over a year ago

uhh yeah. I just typed it in a rush without testing. Variable i in userid[i] is undefined and should have been userid[index]. Updated answer.

Geert-Jan Over a year ago

Btw, the err-message gives you a line-number where the error occurred. Knowing how to interpret the errors goes a long way in solving the problem yourself. Good luck!

T00rk · Accepted Answer · 2014-11-12 11:03:43Z

var EE = require('events').EventEmitter;

var Scraper = function(userId)
{
    this.Emitter = new EE();
    this.userID = userId;
    this.current = -1;
};
Scraper.prototype = 
{
    execute : function()
    {
        var _self = this;
        this.Emitter.on('_requestDone', function(data)
        {
            return _self.computeData(data);
        });
        this.Emitter.on('_errorHappened', function(e)
        {
            return console.log(e);
        });
        return this.sendRequest();
    },
    sendRequest : function()
    {
        this.current++;
        var totalurl = facebookurl + this.userID[this.current];

        var _self = this;
        request(totalurl, function(error, response, html)
        {
            if (!error && response.statusCode == 200)
            {
                return _self.Emitter.emit('_requestDone', html);
            }
            else
            {
                return _self.Emitter.emit('_errorHappened', error);
            }
        });
    },
    computeData : function(data)
    {
        // Perform your actions on data
        if(this.current < this.userID.length)
        {
            return this.sendRequest();
        }
        else
        {
            // When all the array has been computed
        }
    }
};

var S = new Scraper(/* Put your userId Array Here */);
S.execute();

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