根据文件地址下载

//根据文件地址下载
downloads(url){
	let xmlhttp = new XMLHttpRequest();
	 xmlhttp.open("GET", url, true);
	 xmlhttp.responseType = "blob";
	 xmlhttp.onload = function () {
	     if (this.status == 200) {
	     const blob = this.response;
	     const link = document.createElement("a");
	     link.href = window.URL.createObjectURL(blob);
	     link.download = '发票';
	     //此写法兼容可火狐浏览器
	     document.body.appendChild(link);
	     const evt = document.createEvent("MouseEvents");
	     evt.initEvent("click", false, false);
	     link.dispatchEvent(evt);
	     window.URL.revokeObjectURL(link.href);
	     document.body.removeChild(link);
	     }
	 };
	 xmlhttp.send();
 }