data-view-byte-length 
Get the byteLength out of a DataView, robustly.
This will work in node <= 0.10 and < 0.11.4, where there's no prototype accessor, only a nonconfigurable own property.
It will also work in modern engines where DataView.prototype.byteLength has been deleted after this module has loaded.
Example
const dataViewByteLength = require('data-view-byte-length');
const assert = require('assert');
const ab = new ArrayBuffer(42);
const dv = new DataView(ab);
assert.equal(dataViewByteLength(dv), 42);
Tests
Simply clone the repo, npm install, and run npm test