Javascript variable scope outside functions

Question

What is the scope of an array in javascript?

How can I resolve this situation?

var parseXlsx = require('excel');
var arrayURLToSearch = [];
parseXlsx('foo.xlsx', function(err, data) {
  if(err) throw err;
    for(var i=1; i<2; i++){
        arrayURLToSearch[i] = data[i][0];
    }
});
console.log(arrayURLToSearch[0]); -> undefined

How can I print the arrayURLToSearch outside the function?

What do you mean outside the function? what is your exact scenario that you want to acheive? If you have no specific scenario, just put console.log(arrayURLToSearch[0]); after the "for" loop — Sharjeel Ahmed, Mar 20 '17 at 13:03

score 1 · Accepted Answer · answered Mar 20 '17 at 13:03

You cannot. The callback happens at some point in the future that you cannot predict. Try this instead:

var arrayURLToSearch = [];
parseXlsx('foo.xlsx', function(err, data) {
  if(err) throw err;
    for(var i=1; i<2; i++){
        arrayURLToSearch[i] = data[i][0];
    }

console.log(arrayURLToSearch[0]);
});

Mihai Alexandru-Ionut · Answer 2 · 2017-03-20T13:08:41.590

0

Your method is asyncronous, so console.log(arrayURLToSearch[0]); line will be executed before parseXlsx method.

One solution is to use a callback function.

function execute(callback){
   var parseXlsx = require('excel');
   var arrayURLToSearch = [];
   parseXlsx('foo.xlsx', function(err, data) {
     if(err) throw err;
     for(var i=1; i<2; i++){
         arrayURLToSearch[i] = data[i][0];
     }
     callback(arrayURLToSearch);
   });
}
execute(function(arrayURLToSearch){
     console.log(arrayURLToSearch[0]);
});

edited Mar 20 '17 at 13:08

answered Mar 20 '17 at 13:01

Mihai Alexandru-Ionut

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@downvoter, please explain the reason. – Mihai Alexandru-Ionut Mar 20 '17 at 13:02
2

Don't answer garbage questions to rep-farm. – Der Hochstapler Mar 20 '17 at 13:03
perhaps its the 2nd part of your sentence - because `parseXlsx` is called - its the callback. – Daniel A. White Mar 20 '17 at 13:03
thanks for the answer, how i can resolve? – OiRc Mar 20 '17 at 13:03
@OiRc, i will update my answer in few moments. – Mihai Alexandru-Ionut Mar 20 '17 at 13:04

Javascript variable scope outside functions

2 Answers2