Regex to deal with punctuation and text improvement

Question

I'm trying to avoid bad behavior on our app, and it needs me to clean some string from bad usage.

Let's says I have this string

str = "This is a very bad BEHAVIOR !!!Don't you think So ????";

I need to apply 3 rules : - no shout mode (not all CAPS) - Remove space before punctuation, and add one space after - Remove all duplicate punctuation

So my string should be

str = "This is a very bad behavior! Don't you think so?"

I found on stackoverflow a sample code to add one space after punctuation :

str.replace(/[,.!?:;](?=\S)/g, '$& ');

But that does not help me to remove space before punctuation

Help would be really appreciate to find the right Regex

Answer 1

This seems to work -

str.replace(/\s*([,.!?:;])[,.!?:;]*\s*/g,'$1 ').  //This removes all the punctuations
replace(/(?:^|[^a-z])([A-Z]+)(?:[^a-z]|$)/g,function(v){return v.toLowerCase();}). //Upper case to lower case
replace(/\s*$/,"") //Trimming the right end

OUTPUT:
"This is a very bad behavior! Don't you think So?"

EDIT:

Regarding the scenario where decimal points are used (like in case - 'This is 14.5 degree'), using a Negative lookahead(like so - (?!\d+) ) should work.

For Example -

str = 'This is 14.5 degree'
str.replace(/\s*(?!\d+)([,.!?:;])[,.!?:;]*(?!\d+)\s*/g,'$1 ').  //This removes all the punctuations
replace(/(?:^|[^a-z])([A-Z]+)(?:[^a-z]|$)/g,function(v){return v.toLowerCase();}). //Upper case to lower case
replace(/\s*$/,"") //Trimming the right end

OUTPUT:
"This is 14.5 degree"