how to use ajax in cscart - php

Question

<script>
function showHint(str) {
if (str.length == 0) {
document.getElementById("txtHint").innerHTML = "";
return;
} else {
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("txtHint").innerHTML = this.responseText;
}
}
xmlhttp.open("GET", "index.php?dispatch=paysrk.paymod?amount="+str, true);
alert(+str);
xmlhttp.send();
}
}
</script>
i think problem is here.Amount is not geting .url is not working.
index.php?dispatch=paysrk.paymod?amount
Question updates:-
My requirements:
When i click the unsubscribe button status in the database change to "US" and change UNSUBSCRIBE button to SUBSCRIBE. A notification with unsubscription completed

Answer 1

If your request is done from CS-Cart environment please try:
<script>
function showHint(str){
if (str.length == 0) {
document.getElementById("txtHint").innerHTML = "";
return;
} else {
$.ceAjax('request', fn_url('paysrk.paymod'), {
method: 'get',
caching: false,
hidden:true,
data: { 'amount': str },
callback: function(data){
alert(data);
}
});
}
}
</script>

Answer 2

i think your problem is in the url syntax.
the first parameter to pass to the url is after ? and all the other parameters should preceded with &
so your GET url should be like this
index.php?dispatch=paysrk.paymod&amount
xmlhttp.open("GET", "index.php?dispatch=paysrk.paymod&amount="+str, true);

Answer 3

you do exactly like this.
function showHint(str) {
if (str.length == 0) {
document.getElementById("txtHint").innerHTML = "";
return;
} else {
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
if (this.readyState == 4 && this.status == 200) {
document.getElementById("txtHint").innerHTML = this.responseText;
}
}
xmlhttp.open("GET", "index.php?dispatch=paysrk.paymod?amount="+str, true));
alert(+str);
xmlhttp.send();
}
}
</script>