Node JS variable scope with response and http methods

Question

Node JS variable scope with response and http methods

I'm still trying to get the hang of this, but this is confusing for me. So I use http.get and a pipe with the bl module, I want it to change content so I can use it outside the function doesn't work why? I thought with var it would be global within my file and that would allow me to change it.

   var http = require('http');
   var bl = require('bl');

   var url1 = process.argv[2];

   var content;

   http.get(url1, function(response){
      response.pipe(bl(function(err,data){
      return data.toString();

     }));
   });
   console.log(content.length);
   console.log(content);

javascript
node.js

Answer 1

Are you trying to modify content? You never assign anything to it and then you try to access it synchronously (which will almost certainly occur before the get completes). I assume you want to do something more like:

   ...
   var content;
   http.get(url1, function(response){
      response.pipe(bl(function(err,data){
         content = data.toString();
         console.log(content.length);
         console.log(content);
     }));
   });

Answer 2

Node.js is asynchronous, which means that your code beneath your get function will probably get executed BEFORE the code inside your callback function (the function you pass as the second argument).

   var http = require('http');

   var bl = require('bl');

   var url1 = process.argv[2];

   var content;

   http.get(url1, function(response){
      response.pipe(bl(function(err,data){
          // After all callbacks have come back, modify content
          content = data.toString(); // Set the value of content
          console.log(content.length);
          console.log(content);
          return content; 
     }));
   });

   // The callback function in get still hasn't been called!
   console.log(content); // undefined