How to join the string either with a dot, exclamation mark, or a question mark?-CodePudding

I want to convert a string to the sentence case. That is, uppercase the first character in each sentence and lowercase the following characters. I managed to do this. However, after splitting the string and converting it to a sentence case, I need to join it again with a corresponding character.

Here is my code that splits the string into sentences:

const string = "my seNTencE . My sentence! my another sentence. yEt another senTence?   Again my sentence   .";

function splitString(str) {
    str = str.split(/[.!?]/);
    
    for(let i = 0; i < str.length; i  ) {
        str[i] = str[i].trim();
    }
    
    for(let i = 0; i < str.length; i  ) {
        str[i] = str[i].charAt(0).toUpperCase()   str[i].slice(1).toLowerCase();
    }
    
    return str;
}

console.log(splitString(string));

In the return statement, I want to return joined strings. For example, the first sentence must end with a dot, and the second must end with an exclamation mark, etc. How to implement this?

CodePudding user response：

str.split eliminates the result of the regex match from the string. If you want to keep it, you can place the separator in a lookbehind like this:

str.split(/(?<=[.!?])/);

The syntax (?<= ) means the regex will find positions that are preceded by punctuation, but won't include said punctuation in the match, so the split method will leave it in.

As a side note, keep in mind that this function will ruin acronyms, proper nouns, and the word I. Forcing the first letter after a period to be a capital letter is probably fine, but you will find that this function does more harm than good.

CodePudding user response：

Use a regular expression with capture groups. This regex uses the lazy ? modifier so the match will end at the first [!.?], and the global g flag to grab all matches.

const string = "my seNTencE . My sentence! my another sentence. yEt another senTence?   Again my sentence   ."

const rx = /(.*?)([.!?])/g

const found = []
while (m = rx.exec(string)) {
  let str = m[1].trim()
  str = str.charAt(0).toUpperCase()   str.slice(1).toLowerCase()
  found.push(str   m[2])
}

console.log(found)