Code Smell 78 - Callback Hell

Processing an algorithm as a sequence of nested callbacks is not clever.

TL;DR: Don't process calls in a callback way. Write a sequence.

Problems

Readability

Hard to debug.

Complexity

Solutions

Change callbacks to sequence calls.

Extract repeated Code

Refactor.

Sample Code

Wrong

var fs = require('fs');

var fileWithData = '/hello.world';  
fs.readFile(fileWithData, 'utf8', function(err, txt) {  
    if (err) return console.log(err);

    txt = txt + '\n' + 'Add Data!';
    fs.writeFile(fileWithData, txt, function(err) {
        if(err) return console.log(err);
        console.log('Information added');
    });
});

Right

var fs = require('fs');

function logTextWasAdded(err) {  
    if(err) return console.log(err);
    console.log('Information added');
};

function addData(error, actualText) {  
    if (error) return console.log(error);

    actualText = actualText + '\n' + 'Add data';
    fs.writeFile(fileWithData, actualText, logTextWasAdded);
}

var fileWithData = 'hello.world';  
fs.readFile(fileWithData, 'utf8', addData);

Detection

This problem shines at the naked eye. Many linters can detect this complexity and warn us.

Code Smell 06 - Too Clever Programmer

Maxi Contieri ・ Oct 25 '20 ・ 2 min read

#codenewbie #tutorial #beginners

There are two ways to write code: write code so simple there are obviously no bugs in it, or write code so complex that there are no obvious bugs in it.

Tony Hoare