Through : how to output things

[Roelof Wobben]

Hello,

I try to solve a nodeschool exercise where a json file is the input.

So far I have this :

~~~

var combine = require('stream-combiner');
var through = require('through');

module.exports = function() {
   
    var group = through (write,end)
   
    function write(line) {
       
        if (line.length === 0) { return  } ;
        row = JSON.parse(line);
        this.queue(row);
      
    }
       
     function end(row) {
         console.log(row)
         this.queue(null);
     }
   
    return grouper

~~~

but if I do node file.js { 'test' : test } I see no output.

Can someone help me how to output the row variable.

I tried console.log(row) but that did not do the job.

Roelof

[greelgorke]

your module returns undefined because there is no var named grouper. but a group there is

[Ryan Schmidt]

On Jan 19, 2015, at 12:25 PM, Roelof Wobben wrote:
>
> I try to solve a nodeschool exercise where a json file is the input.
>
> So far I have this :
>
> ~~~
>
> var combine = require('stream-combiner');
> var through = require('through');
> module.exports = function() {
>
> var group = through (write,end)
>
> function write(line) {
>
> if (line.length === 0) { return } ;
> row = JSON.parse(line);
> this.queue(row);
>
> }
>
> function end(row) {
> console.log(row)
> this.queue(null);
> }
>
> return grouper
>
> ~~~

If this is the entire file, it is a syntax error because you are missing a closing curly bracket at the end of the file.

You also have exported a function... but where do you invoke that function?

> but if I do node file.js { 'test' : test } I see no output.

Are you trying to supply "{ 'test' : test }" to the script's stdin perhaps? If so, the way to do that on UNIX is:

echo "{ 'test' : test }" | node file.js

[Roelof Wobben]

Op dinsdag 20 januari 2015 04:50:05 UTC+1 schreef ryandesign:

On Jan 19, 2015, at 12:25 PM, Roelof Wobben wrote:
>
> I try to solve a nodeschool exercise where a json file is the input.
>
> So far I have this :
>
> ~~~
>
> var combine = require('stream-combiner');
> var through = require('through');
> module.exports = function() {
>    
>     var group = through (write,end)
>    
>     function write(line) {
>        
>         if (line.length === 0) { return  } ;
>         row = JSON.parse(line);
>         this.queue(row);
>        
>     }
>        
>      function end(row) {
>          console.log(row)
>          this.queue(null);
>      }
>    
>     return grouper
>
> ~~~

If this is the entire file, it is a syntax error because you are missing a closing curly bracket at the end of the file.

You also have exported a function... but where do you invoke that function?

and how do I invoke this function. That is something I did not learn at nodeschool.io at this moment

Roelof

 

[Ryan Schmidt]

Is the code you showed above the entire code of your project?

What are you trying to do?

When you assign something to module.exports, that implies you're trying to create a module. For example, if you have a file hello.js which contains:

module.exports = function (cb) {
cb(null, "Hello!");
}

Then you can use that module in another file, let's say app.js, by writing:

var hello = require('./hello.js');
hello(function (err, result) {
if (err) return console.error(err);
console.log(result);
});

When you run "node app.js" this will output:

Hello!

You can read much more about how modules work by reading:

http://nodejs.org/api/modules.html