node_modules/jszip/node_modules/core-js/modules/es6.date.to-string.js

var DateProto    = Date.prototype
  , INVALID_DATE = 'Invalid Date'
  , TO_STRING    = 'toString'
  , $toString    = DateProto[TO_STRING]
  , getTime      = DateProto.getTime;
if(new Date(NaN) + '' != INVALID_DATE){
  require('./_redefine')(DateProto, TO_STRING, function toString(){
    var value = getTime.call(this);
    return value === value ? $toString.call(this) : INVALID_DATE;
  });
}