(function() {
var uniqueValue = 0;
function next() {
return ++uniqueValue;
}
Constructor = function() {
this.getValue = next;
}

})();

var instance = new Constructor();

has the *desirable* quality that the implementation of getValue (”next”)
is hidden from outside callers. But that quality makes it pretty
difficult to mock in a test environment.

– also, thanks for you post, it helped me a lot in my struggle as a novice javascript coder to figure out how to test it. I think I’m on my way now.

function MyClass()
{
this.result = null;
this.error = null;

this.loadCustomerData = function(customerId, asyncCallback)
{
this.result = null;
this.error = null;

var myClass = this;
this.makeAjaxCall(
“POST”,
“CustomerService.asmx/LoadCustomer”,
“customerId=” + customerId,
function(ajaxResult) {
myClass.result = ajaxResult;
asyncCallback(myClass);
},
function(error){
myClass.error = error;
asyncCallback(myClass);
}
);
}

this.makeAjaxCall = function(type, url, data, successCallback, errorCallback)
{
$.ajax({
type: type,
url: url,
data: data,
success: function(msg){
successCallback(msg.d); // return value from web service
},
success: function(req, status, error){
errorCallback(error); // when error occurs
}
});
}
}

You’re correct… I just overlooked it. I corrected the mistake. Thanks for pointing that out.