use a constant as a error message

Author: zloirock

packages/core-js/internals/array-reduce.js

@@ -6,14 +6,16 @@ var lengthOfArrayLike = require('../internals/length-of-array-like');
 
 var $TypeError = TypeError;
 
+var REDUCE_EMPTY = 'Reduce of empty array with no initial value';
+
 // `Array.prototype.{ reduce, reduceRight }` methods implementation
 var createMethod = function (IS_RIGHT) {
   return function (that, callbackfn, argumentsLength, memo) {
     var O = toObject(that);
     var self = IndexedObject(O);
     var length = lengthOfArrayLike(O);
     aCallable(callbackfn);
-    if (length === 0 && argumentsLength < 2) throw new $TypeError('Reduce of empty array with no initial value');
+    if (length === 0 && argumentsLength < 2) throw new $TypeError(REDUCE_EMPTY);
     var index = IS_RIGHT ? length - 1 : 0;
     var i = IS_RIGHT ? -1 : 1;
     if (argumentsLength < 2) while (true) {
@@ -24,7 +26,7 @@ var createMethod = function (IS_RIGHT) {
       }
       index += i;
       if (IS_RIGHT ? index < 0 : length <= index) {
-        throw new $TypeError('Reduce of empty array with no initial value');
+        throw new $TypeError(REDUCE_EMPTY);
       }
     }
     for (;IS_RIGHT ? index >= 0 : length > index; index += i) if (index in self) {