javascript实现获取字符串hash值

var I64BIT_TABLE = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_-'.split(''); function hash(input){ var hash = 5381; var i = input.length - 1;  if(typeof input == 'string'){  for (; i > -1; i--)   hash += (hash << 5) + input.charCodeAt(i); } else{  for (; i > -1; i--)   hash += (hash << 5) + input[i]; } var value = hash & 0x7FFFFFFF;  var retValue = ''; do{  retValue += I64BIT_TABLE[value & 0x3F]; } while(value >>= 6);  return retValue;}