js流文件下载和生成预览链接

// 附件预览下载
    downloadFile: params => {
        return new Promise((resolve, reject) => {
            axios({
                method: "get",
                url: `${process.env.VUE_APP_BASE_API}/common/downloadFile`, // 请求地址
                params, // 参数
                responseType: "blob", // 表明返回服务器返回的数据类型
                headers: {
                    Authorization: sessionStorage.getItem('loginToken') || ''
                }
            }).then(value => {
                if (params.openOnLine) {
                    let binaryData = [];
                    binaryData.push(value.data);
                    const previewSrc = window[window.webkitURL ? 'webkitURL' : 'URL'].createObjectURL(new Blob(binaryData));
                    resolve(previewSrc)
                } else {
                    let MIME = {
                        jpg: 'image/jpeg',
                        jpeg: 'image/jpeg',
                        png: 'image/png',
                        webp: 'image/webp',
                        xls: 'application/vnd.ms-excel',
                        xlsx: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
                        doc: 'application/msword',
                        docx: 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
                        pptx: 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
                        ppt: 'application/vnd.ms-powerpoint',
                        pdf: 'application/pdf'
                    };
                    let blob = new Blob([value.data], {
                        type: MIME[params.fileType]
                    });
                    let fileName = params.fileName;
                    if (window.navigator.msSaveOrOpenBlob) {
                        navigator.msSaveBlob(blob, fileName);
                    } else {
                        let link = document.createElement('a');
                        link.href = window.URL.createObjectURL(blob);
                        link.download = fileName;
                        link.click();
                        // 释放内存
                        window.URL.revokeObjectURL(link.href);
                    }
                }
            }).catch(err => {
                reject(err);
            });
        })
    },