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auchomage/decon_t2_calledFile.js

Created July 10, 2016 22:26
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Node.JS callbacks - question 1: I have 2 files (1) decon_t2_calledFile.js and (2) decon_t2_callingFile.js. My aim is to take the string output of file 1 (decon_t2_calledFile.js) and access through file 2 (decon_t2_callingFile.js))
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decon_t2_calledFile.js
module.exports = function(callback){
function () {
// Contents of this anonymous function will serve as output
// from this file
console.log('** Output from decon_t2_calledFile.js ** ');
}
};
Raw
decon_t2_callingFile.js
var someInput = require('./decon_t2_calledFile.js');
// display contents of 'decon_t2_calliedFile.js'
someInput(function(callback){
callback();
}); // should display ('** Output from decon_t2_calledFile.js **
@auchomage
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auchomage commented Jul 20, 2016

A callback is generally defined as a function that runs after something else runs.

What does that statement mean in the context of :

//decon_t2_callingFile.js
var someFunction = require('./decon_t2_calledFile.js');

// display contents of  'decon_t2_calliedFile.js'
someFunction(function(myString){
    console.log(myString);
});

What else is happening here? This will help me to identify it in future, as my previous definition of merely placing a function inside another function is wrong.
Thanks Andrew.

@andrewjmead
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andrewjmead commented Jul 20, 2016

That "something else" would be anything asynchronous like fetching a webpage or making a database request. If you have synchronous code, callbacks are really adding any value because a simple return statement could get the job done just fine.

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