在nodejs中使用双引号切片缓冲区时获取额外字符

Im trying to crop a javascript object (stringified) to a determined size (specifically for Apple Push Notification 256 Max), however i just discovered that when my one of the variables have a string that contains double quotes it gets an extra character that mess with the limit, in the following example i replicated it have a 30 size limit Im trying to crop a javascript object (stringif