dijit.form.ValidationTextBox calls validator function twice onBlur - ajax

Question

I have an AJAX call to check the availability of username using Dojo and PHP. Everything is working great, but there is something huge happening behind. Every time I type a word or during onBlur event, dojo makes AJAX call twice and sometimes thrice. I read this link and they say it is fixed since v1.3, I am using v1.7. I tried putting the AJAX function inside setTimeout() and put a 3 secs delay but still the same thing happens. How can prevent that and do only one AJAX call?
var _username = new dijit.form.ValidationTextBox({
name : "{{ username.name }}",
type : "text",
required : true,
invalidMessage : message.invalid.username
}, "{{ username.id }}");
dijit.byId("{{ username.id }}").validator = fnUsernameAvailable;
function fnUsernameAvailable(a) {
if (a === "" )
return false;
dojo.xhrPost({
url : "{{ site_url() }}/ajax/check_username_availability",
handleAs: "json",
content : {
username : a,
csrf_libtracking : fnCsrf()
},
load : function(data) {
_isAvailable = data.result;
}
});
return _isAvailable;
}

Answer 1

You could use a little trick like :
inside you ValidationTextBox, add a property :
var _username = new dijit.form.ValidationTextBox({
_beingChecked: false,
name : "{{ username.name }}",
type : "text",
required : true,
invalidMessage : message.invalid.username
}, "{{ username.id }}");
function fnUsernameAvailable(a) {
if (a === "" || this._beingChecked)
return false;
this._beingChecked = true;
dojo.xhrPost({
url : "{{ site_url() }}/ajax/check_username_availability",
handleAs: "json",
content : {
username : a,
csrf_libtracking : fnCsrf()
},
load : dojo.hitch(this, function(data) {
// _isAvailable = data.result; <-- is this really useful ?
this._beingChecked = false;
dojo.publish("some/topic/to/tell/widgets/it/is/done", [data.result]);
})
});
}
then somewhere in your code, or in your widget you dojo.subscribe to the topic, so that when something is published, you run a function ?

Answer 2

Thanks for the reply. My original plan was to contact the server, check if username is available, via AJAX, and return the var _isAvailable to trigger the invalidMessage property of the ValidationTextBox if the result is false. This would also trigger the tooltip to appear beside the textbox which I wanted to happen.
Pardon for my little knowledge on dojo as this is my first time using this framework.