Error with JavaScript callback functions

After creating a POST route, I encountered unexpected behavior in the code below. The message variable does not display the expected output.

app.post("/", function (req, res, error) {
  var message = "";
  tableSvc.createTable("tableName", function (error, result,response){
      if (error) 
        message += "There was an error in creating this table";
      else 
        message += "Table created succesfully";

  }); 
  console.log(message);     
});

Instead of showing the appropriate messages, an empty string is printed out. Despite executing the callback function and logging it to the console from within that function, the desired strings are not displayed as expected.
This confusion points to my unfamiliarity with JavaScript and callbacks. What might be causing my code to behave unexpectedly?

Answer №1

It appears that the issue lies within the scope of the variable containing the message. Although untested, this approach might yield positive results.

 app.post("/", function (req, res, error) {
    var obj = this;
    obj.message = '';
      tableSvc.createTable("tableName", function (error, result,response){
          if (error) 
            obj.message += "An error occurred while creating the table";
          else 
            obj.message += "Table successfully created";

      }); 

      while(obj.message.length===0){
            ;//Pause execution until the above operation is complete.
      }


      console.log(obj.message);     
    });

Answer №2

Upon further reflection, I realized my initial guess was off the mark as I overlooked the callback execution aspect. It seems that the asynchronous issue mentioned in the other response is likely the cause.

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