test: refactor assert.equal, update syntax to ES6

PR-URL: nodejs#10190
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

test/parallel/test-buffer-arraybuffer.js

@@ -13,9 +13,9 @@ const buf = Buffer.from(ab);
 
 
 assert.ok(buf instanceof Buffer);
-assert.equal(buf.parent, buf.buffer);
-assert.equal(buf.buffer, ab);
-assert.equal(buf.length, ab.byteLength);
+assert.strictEqual(buf.parent, buf.buffer);
+assert.strictEqual(buf.buffer, ab);
+assert.strictEqual(buf.length, ab.byteLength);
 
 
 buf.fill(0xC);
@@ -44,7 +44,7 @@ assert.throws(function() {
 }, TypeError);
 
 // write{Double,Float}{LE,BE} with noAssert should not crash, cf. #3766
-var b = Buffer.allocUnsafe(1);
+const b = Buffer.allocUnsafe(1);
 b.writeFloatLE(11.11, 0, true);
 b.writeFloatBE(11.11, 0, true);
 b.writeDoubleLE(11.11, 0, true);