reverse words in a sentence

reverse.js

let sentence = "Hello World";

function replaceChar(str,targetIndex,newChar){
	return str.substr(0,targetIndex) + newChar + str.substr(targetIndex + 1)
}

function stringReverser(str, startIndex, endIndex) {
  if (!str || str.length < 2) {
    return;
  }
  while (startIndex < endIndex) {
    let tempLeft = str[startIndex];

    str = replaceChar(str, startIndex, str[endIndex]);
    str = replaceChar(str, endIndex, tempLeft);

    startIndex++;
    endIndex--;
  }
  return str;
}


function reverseWords(sentence) {
  // reverse the sentence
  let str_len = sentence.length;
  sentence = stringReverser(sentence, 0, str_len - 1);

  // beginning of our strategy to idenify words
  let start = 0;
  let end = 0;
  while (start < sentence.length) {

    while (sentence[start] === ' ') {
      start++;
    }


    end = start + 1;
    while (end < sentence.length && sentence[end] != ' ') {
      end++;
    }

    // having found the beginning and end of a word, we reverse it in place
    sentence = stringReverser(sentence, start, end - 1);

    start = end;
  }
  return sentence;
}

let result = reverseWords(sentence)
console.log(result);