asyncReplace.js

/**
 * `String.prototype.replace` alternative that supports `async` _replacer_ functions
 * @private
 * @ignore
 * @param {String} str The string to perform a replace on
 * @param {RegExp} regex The regular expression that the replace will match
 * @param {Function} replacer An `async` function that operates the same way as the function passed into `String.prototype.replace`
 */
async function replace(str, regex, replacer) {
  const mtchs = [];
  str.replace(regex, function asyncReplacer(match) {
    mtchs.push({ args: arguments, thiz: this });
    return match;
  });
  var offset = 0, beg, end, rtn;
  for (let mtch of mtchs) {
    rtn = replacer.apply(mtch.thiz, mtch.args);
    if (rtn instanceof Promise) rtn = await rtn;
    if (rtn !== mtch.args[0]) {
      if (!rtn) rtn = String(rtn); // same as async version
      beg = mtch.args[mtch.args.length - 2] + offset;
      end = beg + mtch.args[0].length;
      str = str.substring(0, beg) + rtn + str.substring(end);
      offset += rtn.length - mtch.args[0].length;
    }
  }
  return str;
}