Edit in JSFiddle

var buffer = new ArrayBuffer(80);
//first arguement-> reference to representing buffer
//second arguement-> offset
//third arguement-> size of typed array
var typed_array = new Int16Array(buffer, 0, 40);//created a typed array representing the complete ArrayBuffer

typed_array[0] = 12;
typed_array[39] = 2;

document.getElementById("number").innerHTML = typed_array[0];

<span id="number"></span>