diff --git a/index.js b/index.js
index e0190bf..3ad4c6d 100644
--- a/index.js
+++ b/index.js
@@ -1,24 +1,17 @@
 
 module.exports = function newArray(start, end) {
-    var n0 = typeof start === 'number',
-        n1 = typeof end === 'number'
+  start = +start;
+  end = +end;
+  if (!isNaN(start) && isNaN(end)) {
+    end = start;
+    start = 0;
+  } else if (isNaN(start) && isNaN(end)) {
+    start = end = 0;
+  }
 
-    if (n0 && !n1) {
-        end = start
-        start = 0
-    } else if (!n0 && !n1) {
-        start = 0
-        end = 0
-    }
+  const len = end - start;
+  if (len < 0) throw new Error("array length must be positive");
 
-    start = start|0
-    end = end|0
-    var len = end-start
-    if (len<0)
-        throw new Error('array length must be positive')
-    
-    var a = new Array(len)
-    for (var i=0, c=start; i<len; i++, c++)
-        a[i] = c
-    return a
-}
\ No newline at end of file
+  const a = new Array(len).fill(start).map((x, y) => x + y);
+  return a;
+};