Converting a Buffer to JSON and Utf8 Strings in Nodejs

Nodejs and browser based JavaScript differ because Node has a way to handle binary data even before the ES6 draft came up with ArrayBuffer. In Node, Buffer class is the primary data structure used with most I/O operations. It is a raw binary data that is allocated outside the V8 heap and once allocated, cannot be resized.

Before Nodejs v6.0, to create a new buffer you could just call the constructor function with new keyword:

let newBuff = new Buffer("New String");

To create a new buffer instance, in latest and current stable releases of Node:

let newBuff = Buffer.from("New String");

The new Buffer() constructor have been deprecated and replaced by separate Buffer.from(), Buffer.alloc(), and Buffer.allocUnsafe() methods.

More information can be read through official documentation.

Convert a Buffer to JSON

Buffers can convert to JSON.

let bufferOne = Buffer.from("This is a buffer example.");
console.log(bufferOne);

// Output: <Buffer 54 68 69 73 20 69 73 20 61 20 62 75 66
// 66 65 72 20 65 78 61 6d 70 6c 65 2e>

let json = JSON.stringify(bufferOne);
console.log(json);

// Output: {"type":"Buffer","data":[84,104,105,115,32,105,
// 115,32,97,32,98,117,102,102,101,114,32,101,120,97,109,
// 112,108,101,46]}

The JSON specifies that the type of object being transformed is a Buffer, and its data.

Convert JSON to Buffer

let bufferOriginal = Buffer.from(JSON.parse(json).data);
console.log(bufferOriginal);

// Output: <Buffer 54 68 69 73 20 69 73 20 61 20 62 75 66
// 66 65 72 20 65 78 61 6d 70 6c 65 2e>

Convert Buffer to Utf-8 String

console.log(bufferOriginal.toString("utf8"));

// Output: This is a buffer example.

.toString() is not the only way to convert a buffer to a string. Also, it by defaults converts to a utf-8 format string.

The other way to convert a buffer to a string is using StringDecoder core module from Nodejs API.