JAvascript:文字列の動的置換***

/** 
 *      ***  
 * @val       
 * @head     ，  3
 * @last     ，  4
*/
export const replaceStar = (val, head = 3, last = 4) => {
  if (!val) { //          
    return val;
  }
  if (val.length <= 10) { //               
    last = 0;
  }
  let str = '*';
  let len = val.length - head - last;
  str = str.repeat(len); // *   len 
  let re = new RegExp('(.{' + head + '}).*(.{' + last + '})', ''); //        
  return val.replace(re, '$1'+str+'$2'); //   
};