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POinjecting arguments versus returning data in node.js
 

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  1. POinjecting arguments versus returning data in node.js
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    <p>I'm trying to understand when to inject something like the response into a function, versus calling a function and returning something from it. In Node.js that is.</p> <p>Do any functions in Node.js return data? Or is it all about injecting arguments and using callbacks?</p> <pre><code>var sendHTMLToBrowser = require("../myCode/andrewsHelpers").sendHTMLToBrowser; //var execExternalCommand = require("./childProcesses").execExternalCommand; // import the exec function defined on the child_process module var exec = require('child_process').exec; function start(response, request) { console.log("Request handler 'start' was called"); var body = '&lt;!doctype html&gt;'+ '&lt;html lang="en"&gt;'+ '&lt;head&gt;'+ '&lt;meta charset=UTF-8" /&gt;'+ '&lt;/head&gt;'+ '&lt;body&gt;'+ '&lt;p&gt;Hello Andrew :)&lt;/p&gt;'+ '&lt;/body&gt;'+ '&lt;/html&gt;'; sendHTMLToBrowser(response, body); } function linecount(response, request) { console.log("Request handler 'linecount' was called."); // launch the command "cat *.js | wc -l" exec('cat *.js | wc -l', function(err, stdout, stderr) { // the command exited or the launching failed if (err) { // we had an error launching the process console.log('child process exited with error code', err.code); return; } sendHTMLToBrowser(response, stdout.toString()); }); } function executeCommand(command) { return result; } exports.start = start; exports.linecount = linecount; </code></pre> <p>So I've hardcoded in some code to display the linecount in the browser. What if I wanted to make a more generic function, that took a command as a string and returned the output? Would I again inject response into this function or could I return the result?</p> <p>Is it a question as to whether a command will potentially become a block? e.g. doing some basic string manipulation could probably be implemented as a function that returns a value?</p> <p>thanks.</p>
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    1. UShexacyanide
    1. USmagician11
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    1. COI think what you're looking for is a Templating Engine. Here's a list of node.js supported ones: https://github.com/joyent/node/wiki/modules#wiki-templating
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      1. USWill
    2. COAny function that involves I/O, would require a callback. In your question you are executing an external program so yes it will require a callback.
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      1. POinjecting arguments versus returning data in node.js
      1. USuser568109
    3. COThe subject of your question is a fundamental paradigm of node.js and you will be better served reading tutorials and trying examples whereas stackoverflow is better for specific problems in your code.
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      1. POinjecting arguments versus returning data in node.js
      1. USPeter Lyons
 

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