Node.JS MySQL query nested function returning array

Question

function searchCoords(){
  var result = result;
  connection.query('SELECT * FROM monitoring', function(err, result){
    if(err){
      console.log(err);
    }
    return{
      result: result};
    });
}

That's my code. I'm using that code to find the last coordinates of some devices and display them in google maps. but i need to first be able to access the array from the ouside so i can do something like:

myModule.searchCoords().result

or myModule.searchCoords()().result

However I still can't access the array (result) from the outside function, let alone from another module. I've been reading on closures, scopes, nested functions, anonymous functions, etc. but i still can't find the solution. What am i doing wrong?

Billy Moon · Accepted Answer · 2014-02-04 20:55:05Z

1

Problem is, that the query is asynchronous, so it can't return a value in the normal flow. If you pass a function when you call searchCoords, then that function can be called after the results come back - which could be after a long delay. This is necessary to prevent the program flow from being blocked whilst potentially long operations are in process.

// accept a callback function to execute after getting results...
function searchCoords(callback){
  var result = result;
  connection.query('SELECT * FROM monitoring', function(err, result){
    if(err){
      console.log(err);
    }
    // run the callback function, passing the results...
    callback({result: result});
  });
}

// call like this...
// pass a function accepting results object that will be executed as callback
// once results have been returned...
searchCoords(function(resultsObject){
    console.log(resultsObject.result)
})

answered Feb 4, 2014 at 20:55

Billy Moon

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2 Comments

arrigonfr Over a year ago

thanks, that worked, now i can call the variable from the outside and display it like: database.searchCoords(function(resultsObject){ resultsObject.result; }); there's still one more thing i'd like to do... is there a way to convert the callback function into a variable that will return exactly the same as result so i can call it from the google maps api like: variable[0][1]

Billy Moon Over a year ago

I am not sure exactly what you mean - I think you should perhaps ask a question on stack overflow ;)

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