可以监控下载进度的xhr下载方法

download(options = {}) {
    const {
        url,
        method = 'GET',
        onProgress,
        data = null
    } = options
    return new Promise((resolve, reject) => {
        const xhr = new XMLHttpRequest();
        xhr.addEventListener('readystatechange', () => {
            if (xhr.readyState === xhr.DONE) {
                console.log('下载完成');
                resolve(xhr)
            }
        })
        xhr.addEventListener('progress', (e) => {
            console.log(e.loaded, e.total);
            onProgress && onProgress({
                loaded: e.loaded,
                total: e.total
            })
        })
        xhr.open(method, url)
        xhr.send(data)
    })
}