Web前端js下载流文件

前端下载文件大概有以下种：

1）a标签链接下载

<a href="url">点击链接下载</a>

2）表单form提交下载

var form = $("<form></form>").attr("action", url).attr("method", "post");
        form.append($("<input></input>").attr("type", "hidden").attr("name", "参数1").attr("value", "值1"));
        form.append($("<input></input>").attr("type", "hidden").attr("name", "参数2").attr("value", "值2"));
        form.appendTo('body').submit().remove();
//url为请求地址

3）使用XMLHttpRequest对象下载

var xhr = new XMLHttpRequest();
        var formData = new FormData();
        formData.append('参数1', "值1");
        formData.append('参数2',"值2");
        xhr.open('POST', url, true);
        xhr.setRequestHeader("token", token);     //可以带请求头
        xhr.responseType = 'blob';
        xhr.onload = function (e) {
            if (this.status == 200) {
                var blob = this.response;
                //var responseHeaders = xhr.getAllResponseHeaders();
                //var ContentDisposition = this.getResponseHeader("Content-Disposition");
                //var filename = this.getResponseHeader("Content-Disposition").split('filename=')[1];  
                // 获取文件名，需要在后端响应头暴露("Access-Control-Expose-Headers", "Content-Disposition");

                var filename = "xxxx.xxx";
                if (window.navigator.msSaveOrOpenBlob) {
                    navigator.msSaveBlob(blob, filename);
                } else {

                    blob.type = "application/octet-stream";
                    var url = URL.createObjectURL(blob);
                    var a = document.createElement('a');
                    a.href = url;
                    a.download = filename;
                    a.click();
                    window.URL.revokeObjectURL(url);

                }
            }else if(this.status == 404){
                alert("file does not exist!");
            }else{
                alert("failed to download file! ");
            }

        };
        xhr.send(formData);