core-js/modules/es.array.reduce.js

'use strict';
var $ = require('../internals/export');
var $reduce = require('../internals/array-reduce').left;
var arrayMethodIsStrict = require('../internals/array-method-is-strict');
var arrayMethodUsesToLength = require('../internals/array-method-uses-to-length');
var CHROME_VERSION = require('../internals/engine-v8-version');
var IS_NODE = require('../internals/engine-is-node');

var STRICT_METHOD = arrayMethodIsStrict('reduce');
var USES_TO_LENGTH = arrayMethodUsesToLength('reduce', { 1: 0 });
// Chrome 80-82 has a critical bug
// https://bugs.chromium.org/p/chromium/issues/detail?id=1049982
var CHROME_BUG = !IS_NODE && CHROME_VERSION > 79 && CHROME_VERSION < 83;

// `Array.prototype.reduce` method
// https://tc39.es/ecma262/#sec-array.prototype.reduce
$({ target: 'Array', proto: true, forced: !STRICT_METHOD || !USES_TO_LENGTH || CHROME_BUG }, {
  reduce: function reduce(callbackfn /* , initialValue */) {
    return $reduce(this, callbackfn, arguments.length, arguments.length > 1 ? arguments[1] : undefined);
  }
});