javascript - Ajax Inside For Loop -


in chrome extension writing need validate objects have stored in localstorage against server . created loop sends data each localstorage element , needs response . code this:

 (var key in localstorage) {         if (! condition )                       continue;          var httprequest = new xmlhttprequest();         httprequest.onreadystatechange = function() {             if (httprequest.readystate === 4 && httprequest.response == 200) {                 'key' loop             }         }         };         var url = base_path ;         httprequest.open("post", url);         httprequest.send(some data);                      }

however while debugging seems in ajax response , 'key' loop isn't key need : expecting same key loop matches each ajax call , got same key ajax calls . doing wrong or expecting isn't possible ? thought since ajax inside closure function , values kept in memory or of sort .

extract actual ajax call separate function:

function ajaxcall( key ) {   var httprequest = new xmlhttprequest();   httprequest.onreadystatechange = function() {     if ((httprequest.readystate === 4) && (httprequest.response == 200)) {       'key' loop     }   };   var url = base_path ;   httprequest.open("post", url);   httprequest.send(some data); }  (var key in localstorage) {   if ( condition ) {         ajaxcall( key );   }     }

reason is, creating closure function passed onreadystatechange. functions point same key variable, holds 1 (the last) value ajax calls, after loop finished.

when create separate function (like ajaxcall() in example), create different context each call , hence callbacks point different keys.


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