Using negative conditions, how to remove whitespaces except line and paragraph breaks

Question

One simple way to remove whitespaces in my case is to do like this -

<textarea id="thetext" lines="8" style="width: 100%; height: 8em;">

  hello,          how are you 

i'm    fine


And i hope the same from you


</textarea><br>
<button onclick="whitespaces()">Vanish</button> 

<script>
    function whitespaces() {
        var input = document.getElementById("thetext");
        input.value = input.value
            .replace(/\t{1,}/g, "")
            .replace(/\n{3,}/g, '\n\n')
            .replace(/ {1,}/g, ' ')
            .replace(/^ /gm, '')
            .replace(/ $/gm, '')
            .replace(/^\n{1,}/g, '')
            .replace(/\n{1,}$/g, '');
    }
</script>

However I'm trying to achieve the same objective with negative condition. That is by using minus or something like that. As i'm new to js, i'm not familiar with negative conditions. So can anyone tell me how to use negative condition in this case. The code should look something like this -

function whitespaces() {
    var input = document.getElementById("thetext"); 
    input.value = input.value.replace(all whitespaces [\s] minus linebreak [\n] and paragraph breaks [\n\n])
}

Yes, that is possible. What did you try and what was the problem? — trincot, Apr 11 '22 at 18:23
What have you tried? Community will be frank at you if you just post a problem without showing your effort — Wasiu, Apr 11 '22 at 18:23
Well, Stack Overflow is a place where you have tried something, but it fails. You then research about it, but if nothing comes up, then ask here. — Arnav Thorat, Apr 11 '22 at 19:53
@trincot, Well, I hope the edit fulfills all your requirements. — Kraken, Apr 12 '22 at 06:47
@wasiu, Well, I hope the edit fulfills all your requirements. — Kraken, Apr 12 '22 at 06:47
@Kraken Nope, you still need to provide your HTML or should we assume that everything is in a single div tag — Wasiu, Apr 12 '22 at 22:55

Klaassiek · Accepted Answer · 2022-04-18T21:00:12.943

SOLUTION 1

You can use the following regular expression to match all whitespace characters except newlines.

[^\S\r\n]

That is, not-not-whitespace (the capital S complements) or not-carriage-return or not-newline. Distributing the outer not (i.e., the complementing ^ in the character class) with De Morgan's law, this is equivalent to “whitespace but not carriage return or newline.” Including both \r and \n in the pattern correctly handles all of Unix (LF), classic Mac OS (CR), and DOS-ish (CR LF) newline conventions.

From this stackoverflow answer.

SOLUTION 2

In javascript you can also use a replacer function to check each match and return the replacement string only if it meets certain conditions. The replacer function here checks for each whitespace whether it is a line break.

<textarea id="thetext" lines="8" style="width: 100%; height: 8em;">

  hello,          how are you 

i'm    fine


And i hope the same from you


</textarea><br>
<button onclick="whitespaces()">Vanish</button> 

<script>
    function whitespaces() {
        var input = document.getElementById("thetext");
        var inputVal = input.value;
        inputVal = inputVal.replace(/\s/g, function(match){
            return match === '\n' ? match : '';
        });
        input.value = inputVal;     
    }
</script>

SOLUTION 3

Another possible solution is to first replace all the paragraph breaks and line breaks by some bogus text (without whitespaces). Then do the whitespace replacement. After that convert the bogus texts back to paragraph and line breaks. (Note that since paragraphs are double line breaks, you do not need the line with the paragraph break replacement.)

<textarea id="thetext" lines="8" style="width: 100%; height: 8em;">

  hello,          how are you 

i'm    fine


And i hope the same from you


</textarea><br>
<button onclick="whitespaces()">Vanish</button> 

<script>
    function whitespaces() {
        var input = document.getElementById("thetext");
        var inputVal = input.value;
        inputVal = inputVal.replace(/\n\n/g, "somebogustextforparagraphbreaks");
        inputVal = inputVal.replace(/\n/g, "somebogustextforlinebreaks");
        inputVal = inputVal.replace(/\s{1,}/g, "");
        inputVal = inputVal.replace(/somebogustextforparagraphbreaks/g, "\n\n");
        inputVal = inputVal.replace(/somebogustextforlinebreaks/g, "\n");
        input.value = inputVal;     
    }
</script>

Not sure what you mean. If you already can do this, why post the question? — Klaassiek, Apr 18 '22 at 16:55
I mean I can do that with normal method. As I mentioned I'm exploring to do this with 'except condition', which excludes line and parabreak from whitespaces. — Kraken, Apr 18 '22 at 18:19
Thankyou for your time. I was looking for something like solution 1 which you have mentioned. Also, the reference to solution 1 explains my questions. Thats the thing i'm looking for. Thanks once again. — Kraken, Apr 18 '22 at 21:55

Using negative conditions, how to remove whitespaces except line and paragraph breaks

1 Answers1