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I just started learning Javascript and I am trying to implement a project that came into my mind. The project is a simple text editor that takes a text as an input does some corrections and posts an output with the fixed text.

The input text is imported as an array. Each line of the text is an object property. The inputText is for displaying the default text in the browser inside a div, and the outputText is the one I use for the editing.

inputText = loadStrings("v.txt");
outputText = inputText;

Now the input text has some sentences. The problem is that there are a lot of empty lines in between.

firstLine



secondLine






thirdLine

What I want to achieve, is to remove all empty lines, but one, so the output text looks like:

firstLine

secondLine

thirdLine

I am searching for a solution for almost 3 days now. I have managed to remove ALL empty lines, but that's not what i want. I want to remove empty lines if they are more than one, but don't make any change if there is only one empty line.

This piece of code is one of many i have tried. This will remove ALL empty lines:

(source: Remove empty elements from an array in Javascript )

outputText = outputText.filter(function(e)
 return e.replace(/[rn]+/g, 'n'));

Here is the codepen with all HTML, CSS and the JS code I am using.
https://codepen.io/theokondak/pen/KrNNVz

Try:

outputText = outputText.filter(function(e)
 return e.replace(/[rn]+/g, 'nn'));

I am not sure about the filter function above. but try below one must work.

outputText = outputText.replace(/[rn]+/g, 'nn');

replacing with two new lines is the simplest way. you will get what you want.

Try this regex:

e.replace(/([rn])2,/g, 'nn')});

This will only match two or more consecutive empty lines replacing by an empty line.

My test code:

var lines = 'firstLinennnnsecodLinennnnnnnthirdLine';
/*
firstLine



secondLine






thirdLine
*/
console.log(lines.replace(/([rn])2,/g, 'nn'));

/*
firstLine

secodLine

thirdLine
*/

I don't know if loadStrings leaves newlines at the end of the line or not. I'll assume it does (based on some code I see on this page). If it ends up mangled, please say so.

It is definitely easier to do this on a single string, like Hélio Márcio Filho says. So in your case, where you start with an array, you could just join the array together,replace three or more newlines with just two, then split it back up into lines:

let outputText = inputText.join('').replace(/(?:r?n)3,/g, 'nn').
 split(/n/).map(line => line + "n");

But you can also do it just with filter - you just need to know how many empty lines you just saw, and suppress the extra ones:

let empties = 0;
let outputText = inputText.filter(line => 
 if (line.replace(/[rn]+/, '')) empties = 0;
 else empties++;
 return empties <= 1;
);

The other answers work with a single string, but you're using the loadStrings() function from Processing.js, which gives you an array of strings.

You could convert the array into a single string, or load the file as a single string, but it seems simplest to me if you just process the array. Something like this:

function reduceNewlines(inputArray)

 var outputNewArray = ;
 var previousLineWasNewline = false;

 for(var i = 0; i < myArray.length; i++)
 if(myArray[i] == '')
 if(!previousLineWasNewline)
 outputArray.push('');
 
 previousLineWasNewline = true;
 
 else
 outputArray.push(myArray[i]);
 previousLineWasNewline = true;
 
 
 return outputArray;

Please note that I haven't tested this code, and there is probably a ton of room for improvement. But the general idea is there: you could write a function that processed the array and returned a new array with the consecutive newlines removed.

You might also consider pre-processing your text file so you don't have to do this at all.

First of all, I would like to thank everyone for trying to help. I studied all your replies, I've tested each of them and they all work (some with needed tweaking) as stand-alone code, but when I inserted them into my code, some things went wrong. So I struggled and came out with my own solution, which is greatly inspired by your comments.

So the code that worked in my case is :

function reduceNewlines(outputTextEditNewLines) 

 for (let key = 0; key < outputTextEditNewLines.length; key++) 
 if (outputTextEditNewLines[key] == '') outputTextEditNewLines[key] = 'n';
 else outputTextEditNewLines[key] = outputTextEditNewLines[key];
 

 arrayToString = outputTextEditNewLines.join(""); // convert object myArray to string
 console.log(arrayToString.replace(/([rn])1,/g, 'nn')); // exports the text as it should

 return arrayToString.replace(/([rn])1,/g, 'nn');

The console.log exports the text as it should. Now the next step for my project is to make this string print to the DOM as it prints in the console.log.