Заменить пробелы в строке запятой

const input = '1529954897.543 GET 200 173481 174274 "https://www.facebook.com/" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) HeadlessChrome/67.0.3391.0 Safari/537.36" "-" 1 0'

let result = input.split(`"`)
  .map((part, i) => i % 2 ?
    part :
    part.split(" ").join(",")
  ).join(`"`)

console.info(result)

function parsestr(str) {
  var tokens = [], i, ch, token = "", in_quote = false;
  for (i = 0; i < str.length; i++) {
    var ch = str.charAt(i);
    if (ch === '"') {
      in_quote = !in_quote;
    } else if (ch === ' ' && in_quote === false) {
      tokens.push(token);
      token = "";
    } else {
      token += ch;
    }
  }
  if (token) {
    tokens.push(token);
  }
  return tokens;
}
var str = '1529954897.543 GET 200 173481 174274 "https://www.facebook.com/" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) HeadlessChrome/67.0.3391.0 Safari/537.36" "-" 1 0'
console.info(parsestr(str));