Question

Below I have a sentance and desiredResult for the sentance. Using the pattern below I can snag the t T that needs to be changed to t, t but I don’t know where to go further.

var sentence = "Over the candidate behaves the patent Then the doctor.";
var desiredResult = "Over the candidate behaves the patent, then the doctor.";
var pattern = /[a-z]\s[A-Z]/g;

I want to a correct sentence by adding comma and a space before a capital other than ‘I’ if the preceding letter is lowercase.

Answer 1

Use .replace() on your sentence and pass replacing function as second parameter

var corrected = sentence.replace(
    /([a-z])\s([A-Z])/g, 
    function(m,s1,s2){  //arguments: whole match (t T), subgroup1 (t), subgroup2 (T)
        return s1+', '+s2.toLowerCase();
    }
);

As for preserving uppercased I, there are many ways, one of them:

var corrected = sentence.replace(
    /([a-z])\s([A-Z])(.)/g, 
    function(m,s1,s2,s3){
        return s1+((s2=='I' && /[^a-z]/i.test(s3))?(' '+s2):(', '+s2.toLowerCase()))+s3;
    }
);

But there are more cases when it will fail, like: His name is Joe., WTF is an acronym for What a Terrible Failure. and many others.