<select name="status[]" multiple>
var form_data = new FormData(this_form);
console.log(form_data);
let sendData = {}, sendDataIndex = {},
postData = new FormData(form);
for(const pair of postData.entries()) {
if (postData.getAll(pair[0]).length > 1) {
pair[0] = pair[0].replace(/\[\]/, "");
if (sendDataIndex[pair[0]] === undefined) {
sendDataIndex[pair[0]] = 0;
} else {
sendDataIndex[pair[0]]++;
}
pair[0] += "[" + sendDataIndex[pair[0]] + "]";
}
sendData[pair[0]] = pair[1];
}