Index loop does not change [duplicate]

Question

I'm trying to gather tweets from twitter, on console if I choose 5 tweets to gather it displays every one of them but if I choose the mysql module to insert them into a database it inserts the last line 5 times.

Can't figure out how to resolve it.

Asking again, had no luck in the last 3 hours making this script work. Was pointed out to for loop does not change index inside function . Can someone please help me fix this problem?

for (var i = 0; i < data.length ; i++) { // get all the messages from username, devfined in search term
  var retweetId_str = data[i].id_str; // id_str = id not rounded more precise
  console.log('id_str:', retweetId_str); // 

 //id_str: 656087507604402176
 //id_str: 656063345192255488
 //id_str: 656063056947126272
 //id_str: 656062911530606592
 //id_str: 656062750574182400     
  con.query('SELECT retweetid_str FROM droid_retweets WHERE retweetId_str=?', retweetId_str, function(error,result){ 
    console.log('id_str:', retweetId_str);         

    //id_str: 656062750574182400
    //id_str: 656062750574182400
    //id_str: 656062750574182400
    //id_str: 656062750574182400
    //id_str: 656062750574182400
  }); 
} // for close

check docs, query is probably an async method so by the time the queries run, retweetId_str is always 656062750574182400 — juvian
– juvian, Commented Oct 19, 2015 at 18:18

Community · Accepted Answer · 2017-05-23 12:16:38Z

1

It's because of closures in javascript.

This answer should help explain it and there are a couple ways to handle it.

The easiest being to use .forEach()

data.forEach(function(d) { // get all the messages from username, devfined in search term

            var retweetId_str = d.id_str; // id_str = id not rounded more precise
            console.log('id_str:', retweetId_str); // 
           con.query('SELECT retweetid_str FROM droid_retweets WHERE retweetId_str=?', retweetId_str, function(error,result){ 
           console.log('id_str:', retweetId_str);         

          }); 

    }); // for close

edited May 23, 2017 at 12:16

CommunityBot

11 silver badge

answered Oct 19, 2015 at 18:21

Catfish

19.4k60 gold badges216 silver badges359 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

user1106925 Over a year ago

It's not because of closures. It's because how variables are scoped.

Alex _TNT Over a year ago

Finally an example that works. Thank you very much. You don't know how grateful I am.

Alex _TNT Over a year ago

I'll add this as an answer in 4min, Thanks again

user1106925 Over a year ago

@Alex_TNT: The answer you were linked to in your previous question and here give this exact solution.

Alex _TNT Over a year ago

It might mean the exact solution for you that might be fluent in javascript but for me as a beginner and only experience I have is with html and 2d/3d graphic designing it's not the same solution.

|

user3589262 · Accepted Answer · 2015-10-19 18:20:30Z

1

It's because the for loop has executed all the iterations before you get response from con.query, that's why it prints the last one several times, because the index is at the last position

answered Oct 19, 2015 at 18:20

user3589262

411 silver badge5 bronze badges

1 Comment

Alex _TNT Over a year ago

I did understand that but I don't know how to implement in my example

Collectives™ on Stack Overflow

Index loop does not change [duplicate]

2 Answers 2

8 Comments

1 Comment

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

8 Comments

1 Comment

Linked

Related