How to avoid last comma when adding json with fs.createWriteStream in nodeJS

Question

I'm using fs.createWriteStream() to add JSON-data asynchronously to a file with file.write(JSON.stringify(data) + ","). So every json-object is followed by a comma. How can I avoid/remove the comma after the last json-object inside the code?

{"key1":"value1"}, {"key2":"value2"},