Requirements: front-end download a file, call the back-end interface to download, if the back-end error need to give an error message if there is no error can be downloaded properly.
solution:
Option One: the first thought is divided into two interfaces First, ask if you can download, if you can go download download
Option II: native ajax request via a state code to distinguish
xhrGet function (type, URL, Fn) {
// the XMLHttpRequest object is used to exchange data with the server in the background
var = new new XHR the XMLHttpRequest ();
xhr.open (type, URL, to true);
xhr.setRequestHeader ( 'X--Requested- with ',' the XMLHttpRequest ');
xhr.setRequestHeader (' the Accept ',' file application / JSON, text / Plain, * / * ');
xhr.onreadystatechange = function () {
// the readyState == request. 4 has been completed
if (xhr.readyState == this.HEADERS_RECEIVED) {
IF (xhr.getResponseHeader ( 'the Type-the Content') == 'file application / vnd.openxmlformats-officedocument.spreadsheetml.sheet') {
xhr.abort ();
the window.location. URL = the href;
return;
}
}
if (xhr.readyState == 4 && xhr.status == 200) {
// 从服务器获得数据
try{
let res = JSON.parse(xhr.responseText);
if(res.rc=='9'){
window.location.href=location.protocol+"//"+location.host+'/api/account/home?url='+encodeURIComponent(location.protocol+"//"+location.host+'/#/home');
return;
}
if(res.rc=='3'){
window.location.href="#/403";
return;
}
fn.call(this, res);
}catch (error){
}
}
};
xhr.send();
}
Our method of callback function onreadystatechange readyState is, identify different readyState status, when readyState == this.HEADERS_RECEIVED, namely the head of the corresponding server has returned, then we get the head of the content-type, if it is application / json is wrong information, the normal operation. If you downloaded the file corresponding to the content-type, such as excel file as 'application / vnd.openxmlformats-officedocument.spreadsheetml.sheet', we give up the time, direct access to the Download the file to download normal.
Readystate attach various stages of status information.
