js异步下载文件请求

注意 ：通常下载文件是用get请求

window.location.href=url;

但是 我们需要下载完成监听，所以必须要异步执行、用常规的ajax是不可以的。我们要用blob对象来实现
1.原生的如何实现

function loadDown(query) {
        var url = "${ctx}/bill/billExport"+query;
        var xhr = new XMLHttpRequest();
        xhr.open('GET', url, true);    // 也可以使用POST方式，根据接口
        xhr.responseType = "blob";
        xhr.onload = function () {
            if (this.status === 200) {
                $('#loadingModal').modal('hide');
                var content = this.response;
                var aTag = document.createElement('a');
                var blob = new Blob([content]);
                var headerName = xhr.getResponseHeader("Content-disposition");
                var fileName = decodeURIComponent(headerName).substring(20);
                aTag.download = fileName;
                aTag.href = URL.createObjectURL(blob);
                aTag.click();
                URL.revokeObjectURL(blob);
            }
        };
        xhr.send()
    }

2 ajax如何实现

$.ajax({
            url:options.url,
            // dataType:"text",
            // type:"get",
            success:function(result){
                var content = this.response;
                var aTag = document.createElement('a');
                var blob = new Blob([content]);
                var headerName = xhr.getResponseHeader("Content-disposition");
                var fileName = decodeURIComponent(headerName).substring(20);
                aTag.download = fileName;
                aTag.href = URL.createObjectURL(blob);
                aTag.click();
                URL.revokeObjectURL(blob);
            }
        })

后台：

response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(filename,"UTF-8"));

参考博客：https://blog.csdn.net/Concsdn/article/details/79961295

https://blog.csdn.net/weixin_38661747/article/details/80754258