The difference between post and get requests for Ajax

GET request

Document.queryselector (' button '). Onclick=function () {
var txt=document.queryselector (' input '). Value;
var xhr=new xmlhttprequest ();
Xhr.open (' Get ', ' 03-fasongshuju.php?msg= ' +txt);
Xhr.setrequestheader (' Content-type ', ' text/html ');
Xhr.send (NULL);
Xhr.onreadystatechange=function () {
if (xhr.readystate==4&&xhr.status==200) {
var Re=xhr.responsetext;
Document.queryselector (' div '). Innerhtml=re;
// }
// }
// }
POST request:

Document.queryselector (' button '). Onclick=function () {
var txt=document.queryselector (' input '). Value;
var xhr=new xmlhttprequest ();
Xhr.open (' Post ', ' 03-fasongshujupost.php ');
Xhr.setrequestheader (' Content-type ', ' application/x-www-form-urlencoded ');//post this piece is different.
Xhr.send (' msg= ' +txt);//This piece is not the same
Xhr.onreadystatechange=function () {
if (xhr.readystate==4&&xhr.status==200) {
var Yaru=xhr.responsetext;
Document.queryselector (' div '). Innerhtml=yaru;
}
}
}

The difference between post and get requests for Ajax