Web前端js下載流文件

前端下載文件大概有以下種：

1）a標簽鏈接下載

<a href="url">點擊鏈接下載</a>

2）表單form提交下載

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

3）使用XMLHttpRequest對象下載

var xhr = new XMLHttpRequest();            
        var formData = new FormData();            
        formData.append('參數1', "值1");            
        formData.append('參數2',"值2");            
        xhr.open('POST', url, true);           
        xhr.setRequestHeader("token", token);     //可以帶請求頭   
        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];  
                // 獲取文件名，需要在後端響應頭暴露("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);