refactor: apply suggestions from code review

Author: headlessNode

lib/node_modules/@stdlib/ndarray/flatten-by/lib/main.js

@@ -40,6 +40,11 @@ var emptyLike = require( '@stdlib/ndarray/empty-like' );
 var ndarray = require( '@stdlib/ndarray/ctor' );
 var format = require( '@stdlib/string/format' );
 
+// VARIABLES //
+
+var ROW_MAJOR = 'row-major';
+var COL_MAJOR = 'column-major';
+
 
 // MAIN //
 
@@ -77,10 +82,14 @@ var format = require( '@stdlib/string/format' );
 */
 function flattenBy( x, options, fcn, thisArg ) {
 	var nargs;
+	var view;
 	var opts;
 	var ctx;
+	var xsh;
 	var cb;
+	var st;
 	var y;
+	var o;
 
 	if ( !isndarrayLike( x ) ) {
 		throw new TypeError( format( 'invalid argument. First argument must be an ndarray-like object. Value: `%s`.', x ) );