Convert uploaded file to array buffer

I would like to share some code snippet which will convert uploaded file to array buffer which we used mostly when upload something to SharePoint using JavaScript. Below is the code snippet for conversion,

var imageAsArrayBuffer;

//Get files from upload control 
var files = document.getElementById("picturefile").files;

fileData = new Blob([files[0]]);
var promise = new Promise(getBuffer);
promise.then(function(data) {       
     imageAsArrayBuffer = data;
}).catch(function(err) {
       alert('Error: ',err);
});

function getBuffer(resolve) {
var reader = new FileReader();
reader.readAsArrayBuffer(fileData);
reader.onload = function() {
 var arrayBuffer = reader.result
 //var bytes = new Uint8Array(arrayBuffer);
 resolve(arrayBuffer);
}

}