javascript - Global variables and asynchronous data -

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i have problem global variable n:

var n ;  socket.on('connect', function(){  socket.on('news', function  (mensaje) {   n = mensaje.data;  $('#string').val(n);  //  show  data    });      $('#string1').val(n);    // can't see anything, why?   ...});  //

first, global variable n shows inside socket.on want show out function.

the problem socket.on has not finished (or invoked callback) when problematic line executes. because on asynchronous operation: returns immediately , invokes callback "later" when data received. data can used after on callback run.

here example of execution order, 1 "runs" before 2, before 3, etc.:

// 1 var n; socket.on('connect', function(){   // 2   socket.on('news', function  (mensaje) { // "on callback"     // 4     n = mensaje.data;     // 5     $('#string').val(n);   });   // 3 - note occurs *before* 4 & 5   //     run in asynchronous callback   //     n has not been assigned yet   $('#string1').val(n); })

the solution only use variable after has been assigned, guaranteed after on callback runs. (promises make easy chain bunch of dependent asynchronous operations.)


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