可以传参的文件下载

postFile(params, url) {
var form = document.createElement("form");
form.style = "display:none;";
form.action = url;
form.method = "post";
form.target = "form_iframe"
document.body.appendChild(form);
if(!document.getElementById("form_iframe")){
var ifreame = document.createElement("iframe")
ifreame.id = "form_iframe";
ifreame.name = "form_iframe";
ifreame.style ="display:none;"
document.body.appendChild(ifreame);
}
// 动态创建input并给value赋值
for (var key in params) {
var input = document.createElement("input");
input.type = "hidden";
input.name = key;
input.value = params[key];
form.appendChild(input);
}
form.submit();
form.remove();
}