add content for buffers

Author: jjmax75

buffers-and-streams/buffers.md

@@ -6,6 +6,55 @@ url: buffers
 
 ## Buffers
 
-### Usage
+Node's `Buffer` class enables working with binary data in Javascript. A buffer is allows a programme to store data temporarily outside the V8 engine's stack.
+
+Though not entirely accurate we can think of a buffer as an array of bytes, each byte is represented by a hexadecimal digit.
 
 The Node `Buffer` class is a global class and therefore does not need to be imported into a module.
+
+### A simple example
+
+```javascript
+// create a buffer from a string
+const myBuffer = Buffer.from("hello node buffers");
+
+console.log(myBuffer);
+// <Buffer 68 65 6c 6c 6f 20 6e 6f 64 65 20 62 75 66 66 65 72 73>
+
+console.log(myBuffer[0]);
+// 104 - unicode char code for h (decimal representation of hex number 68)
+
+console.log(myBuffer.toString());
+// hello node buffers
+```
+
+## Instantiating a Buffer
+
+Buffers can be instantiated with:
+
+- a string
+- an array
+- another Buffer
+- an arrayBuffer
+- an object
+
+using `Buffer.from()`.
+
+Buffers can also be instantiated by size using `Buffer.alloc()`, `Buffer.allocUnsafe()` and `Buffer.allocUnsafeSlow()`
+
+> _Unsafe_ as the memory containing the buffer is not initialised - i.e. not zeroed-out, so the potential exists for sensitive data to be leaked.
+
+```
+const myBuffer1 = Buffer.from([1, 2, 3]);
+console.log(myBuffer1.length);
+// 3
+
+const myBuffer2 = Buffer.alloc(3);
+console.log(myBuffer2);
+// <Buffer 00 00 00>
+
+// allocate a size for the buffer and give each byte an initial value 'a'
+const myBuffer3 = Buffer.alloc(3, 'a');
+console.log(myBuffer3);
+// <Buffer 61 61 61>
+```