Instead of a standard alert in client script, we can use window.confirm to get OK and Cancel options in the alert.
let waiveShipping = currentRecord.getValue({ fieldId:fieldid})
let options = “Are you sure you want to waive shipping? Please enter the reason.”;
if (waiveShipping) {
//It works when clicks ok in the alert
if (window.confirm(options)) {
return true;
}
else {
//it works when cancel clicks in the alert
currentRecord.setValue({
fieldId: fieldid,
value: false
});
return true;
}
}