Access to XMLHttpRequest at 'file:///D:/vue/vue-first/data.json' from origin 'null' has been blocked by CORS policy

回答: 这个错误是由于浏览器的CORS策略引起的。CORS是一种安全机制，用于限制跨域请求。当浏览器发现请求的源与目标不在同一个域时，会发送一个预检请求，检查目标服务器是否允许跨域请求。如果目标服务器没有正确配置CORS头部，浏览器就会拒绝该请求，从而导致这个错误。\[1\]\[2\]

对于你提到的具体错误，'file:///D:/vue/vue-first/data.json'是一个本地文件路径，而'null'是请求的源。由于这是一个本地文件请求，而不是通过HTTP协议请求，所以CORS策略不适用于这种情况。因此，你可以通过将数据文件放在与你的应用程序相同的域中，或者使用服务器来提供数据，以避免这个错误。
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