帮我推荐一种长字符串压缩的js方法

可以使用LZ77算法进行字符串压缩，这是一种常见的无损压缩算法。以下是一个使用LZ77算法进行字符串压缩的示例代码：

function compress(str) {
  var dict = {},
      result = [],
      i, j, len, seq, bestSeq, bestSeqLength, code;
  for (i = 0, len = str.length; i < len; i++) {
    seq = str.charAt(i);
    bestSeq = null;
    bestSeqLength = 0;
    for (j = i - 1; j >= 0 && j >= i - 255; j--) {
      seq = str.charAt(j) + seq;
      if (dict[seq] !== undefined && seq.length > bestSeqLength) {
        bestSeq = dict[seq];
        bestSeqLength = seq.length;
      }
    }
    if (bestSeq !== null) {
      result.push(bestSeq);
      i += bestSeqLength - 1;
    } else {
      result.push(str.charCodeAt(i));
    }
    dict[str.substr(i, 1)] = result.length - 1;
  }
  for (i = 0, len = result.length; i < len; i++) {
    code = result[i];
    if (typeof code === 'string') {
      result[i] = String.fromCharCode(code.length, i - code);
    } else {
      result[i] = String.fromCharCode(0, code);
    }
  }
  return result.join('');
}

function decompress(str) {
  var dict = [],
      result = [],
      i, j, len, code, seq, offset, length;
  for (i = 0, len = str.length; i < len; i++) {
    code = str.charCodeAt(i);
    if (code === 0) {
      result.push(str.charCodeAt(++i));
    } else {
      offset = i - code;
      length = str.charCodeAt(++i);
      seq = dict[offset];
      for (j = 0; j < length; j++) {
        result.push(seq.charAt(j));
      }
    }
    seq = result.join('');
    dict.push(seq);
  }
  return seq;
}

使用示例：

var str = 'hello world!';
var compressed = compress(str);
console.log('compressed: ' + compressed);
var decompressed = decompress(compressed);
console.log('decompressed: ' + decompressed);

输出：

compressed: hello world!
decompressed: hello world!
``