javascript - node.js : Variables outside of functions -

i'm new nodejs , trying figure out stuff unfortunately couldn't find information on knowledge.

basicly, want use variable function inside function wich child of main function.

here code :

http.get(url, function(res) { var body = '';  res.on('data', function(chunk) {     body += chunk; });  res.on('end', function() {     var jsonresult = json.parse(body);     (var i=0;i<5;i++)     {         gameid = jsonresult.gamelist[i].gameid;         url = 'http://somesite.com/' + gameid + '/0/token';         http.get(url, function(res) {             var body = '';              res.on('data', function(chunk) {                 body += chunk;             });              res.on('end', function() {                 jsonres = json.parse(body);                 switch(i)                 {                     case 0:                         var elo0 = jsonres.interestscore;                         module.exports.elo0 = elo0;                         break;                     case 1:                         var elo1 = jsonres.interestscore;                         module.exports.elo1 = elo1;                         break;                     case 2:                         var elo2 = jsonres.interestscore;                         module.exports.elo2 = elo2;                         break;                     case 3:                         var elo3 = jsonres.interestscore;                         module.exports.elo3 = elo3;                         break;                     case 4:                         var elo4 = jsonres.interestscore;                         module.exports.elo4 = elo4;                         break;                  }           });         }).on('error', function(e) {             console.log("got error: ", e);         });      }  }); }).on('error', function(e) {   console.log("got error: ", e); }); 

note didn't include everything, problematic part. want use variable loop inside switch doesn't work.

the problem here referencing i in switch statement within asynchronous callback. when this, won't value of @ time function created, final value of @ end of loop iteration.

there couple of ways fix - both involve trapping current loop value of in closure later reference callback.

for example:

for (var i=0;i<5;i++) {     (function(idx) {         gameid = jsonresult.gamelist[idx].gameid;         url = 'http://somesite.com/' + gameid + '/0/token';         http.get(url, function(res) {             ...              res.on('end', function() {                 jsonres = json.parse(body);                 switch(idx)                 {                     case 0:                       break;                      ...                 }             });             ...         });     })(i); } 

here, anonymous function created each pass through loop , called passing current value of loop counter i incoming parameter idx.

another approach (as mentioned in comments above) refactor inner part of loop separate function , call passing necessary context:

function scorehandler(jsonresult, idx) {     var gameid = jsonresult.gamelist[idx].gameid;     var url = 'http://somesite.com/' + gameid + '/0/token';     http.get(url, function(res) {         ...          res.on('end', function() {             jsonres = json.parse(body);             switch (idx) {                ...             }         });     })     .on('error', function(e) {         console.log("got error: ", e);     }); } 

your refactored loop like:

res.on('end', function() {     var jsonresult = json.parse(body);     (var = 0; < 5; i++) {         scorehandler(jsonresult, i);     } });