Configring node js.

node_modules/core-js/modules/_to-index.js

@@ -0,0 +1,7 @@
+var toInteger = require('./_to-integer')
+  , max       = Math.max
+  , min       = Math.min;
+module.exports = function(index, length){
+  index = toInteger(index);
+  return index < 0 ? max(index + length, 0) : min(index, length);
+};