js 获取页面header值

var xhr = new XMLHttpRequest();
xhr.open('GET', 'https://example.com/api/data', true);

xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
        var headers = xhr.getAllResponseHeaders();
        console.log(headers); // 打印所有响应头

        // 获取特定的响应头
        var contentType = xhr.getResponseHeader('Content-Type');
        console.log(contentType);
    }
};

xhr.send();

fetch('https://example.com/api/data')
    .then(response => {
        // 获取所有响应头
        var headers = response.headers;
        console.log(headers);

        // 获取特定的响应头
        return response.text().then(text => {
            var contentType = response.headers.get('Content-Type');
            console.log(contentType);
            return text;
        });
    })
    .then(data => {
        console.log(data); // 打印响应体
    })
    .catch(error => {
        console.error('Error:', error);
    });

app.use((req, res, next) => {
    res.header('Access-Control-Allow-Origin', '*');
    res.header('Access-Control-Expose-Headers', 'Content-Type, Authorization');
    next();
});