按后缀合并列表元素

function mergeBySuffix(list) {
  let mergedList = [];
  let suffixes = {};

  for (let i = 0; i < list.length; i++) {
    let item = list[i];
    let suffix = item.substring(item.lastIndexOf('.') + 1);

    if (suffixes.hasOwnProperty(suffix)) {
      suffixes[suffix].push(item);
    } else {
      suffixes[suffix] = [item];
    }
  }

  for (let suffix in suffixes) {
    let mergedItem = suffixes[suffix].join(', ');
    mergedList.push(mergedItem);
  }

  return mergedList;
}

// 示例用法
let list = ['file1.jpg', 'file2.jpg', 'file3.png', 'file4.txt', 'file5.txt'];
let mergedList = mergeBySuffix(list);
console.log(mergedList);
// 输出：['file1.jpg, file2.jpg', 'file3.png', 'file4.txt, file5.txt']