javascript - 我无法从 html 中的单独文件访问变量

我正在尝试填充下拉框，但当我引用所有货币时，我总是收到未定义错误。

此代码是第三方提供给我的，用于实现填充保管箱和编辑一些文本的简单目标，我不知道为什么我需要引用的 js 文件中的变量是即将到来无敌

var allCurrencies = {
  "AED": "United Arab Emirates Dirham",
  "BTC": "Bitcoin",
  "CAD": "Canadian Dollar",
  "EUR": "Euro",
  "JPY": "Japanese Yen",
  "RUB": "Russian Ruble",
  "USD": "United States Dollar"
};

// Initial data for exchange rates
var exchangeRates = {
  "disclaimer": "Usage subject to terms: https://openexchangerates.org/terms",
  "license": "https://openexchangerates.org/license",
  "timestamp": 1534107604,
  "base": "USD",
  "rates": {
    "BTC": 0.000157753542,
    "CAD": 1.316853,
    "EUR": 0.879353,
    "JPY": 110.46550427,
    "USD": 1,
  }
};

/* Your solution goes here */

<head>
   <meta charset="UTF-8">
   <title>Currency Exchange</title>
   <script src="jquery-3.2.1.min.js"></script>
   <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
   <link href="style.css" rel="stylesheet">
   <script src="currex.js" defer></script>
   <script>

   </script>
</head>

我只是在寻找任何可以帮助解决这个问题的起点

最佳答案