node_modules/jszip/node_modules/core-js/modules/_add-to-unscopables.js

// 22.1.3.31 Array.prototype[@@unscopables]
var UNSCOPABLES = require('./_wks')('unscopables')
  , ArrayProto  = Array.prototype;
if(ArrayProto[UNSCOPABLES] == undefined)require('./_hide')(ArrayProto, UNSCOPABLES, {});
module.exports = function(key){
  ArrayProto[UNSCOPABLES][key] = true;
};