Mocking jQuery Ajax Calls with Random Templated Data

In a recent blog post, Mocking the jQuery Ajax Call in ASP.NET MVC 3 Music Store , I showed you how you could use the $.mockjax library, written by Jonathan Sharp, to intercept AJAX requests and return a mocked response. This tool can be especially useful when trying to code your front-end, while the back-end piece is either isn’t available or accessible.

Another useful library that you may consider when building quick prototypes is $.mockJSON, written by Menno van Slooten. This library has some of the same features as $.mockjax, but the piece I’d like to focus on is the random data tempting feature. This can be very handy when you want to mock a JSON response from a AJAX call, but instead of manually building the response you can build a template to do it for you.

To demonstrate using this random data technique, I decided to use the SlickGrid jQuery Plugin and populate it with the JSON response from an AJAX call. Since the AJAX call doesn’t exist, I am going to use $.mockjax to return the response using random data generated from $.mockJSON.

The following code is what is necessary to populate the SlickGrid with data from an AJAX call.

<pre>(function($) {

var grid,
columns = [
{id:”firstName”, name:”First Name”, field:”firstName”, width:70},
{id:”lastName”, name:”Last Name”, field:”lastName”, width:70},
{id:”email”, name:”Email”, field:”email”, width:170},
{id:”percentHealth”, name:”% Health”, field:”percentHealth”, width:90, formatter:GraphicalPercentCompleteCellFormatter},
{id:”birthday”, name:”Birthday”, field:”birthday”, width:70},
{id:”married”, name:”Married”, field:”married”, width:50, formatter:BoolCellFormatter}
options = {
editable: false,
enableAddRow: false,
enableCellNavigation: true,
rowCssClasses: function(item) {
return (item.percentHealth >= 80) ?
“healthy” : “”;

url: “/Contact/List”,
type: “GET”,
dataType: “json”,
success: function(data, textStatus, xhr) {
grid = new Slick.Grid(“#myGrid”,
data.contacts, columns, options);
error: function(xhr, textStatus, errorThrown) {
console.log(“Error: “ + textStatus);

function BoolCellFormatter(row, cell, value,
columnDef, dataContext) {
return value ? “✔” : “”;

</pre>At this point, I don’t have the '/Contact/List' endpoint defined so if I executed the above code I would get a GET 404 (NOT FOUND) error in my console. If I did want to test the behavior of my front-end without depending on a back-end existing, then I can add an additional $.mockjax statement to intercept the call and respond with some random data provided by $.mockjson.

url: ‘/Contact/List’,
responseTime: 750,
responseText: $.mockJSON.generateFromTemplate({
50-500”: [{
0-1”: true,
“email” : “@EMAIL”,
“firstName”: “@MALE_FIRST_NAME”,
“lastName”: “@LAST_NAME”,
“birthday”: “@DATE_MM/@DATE_DD/@DATE_YYYY”,
0-100”: 0
</pre>The above code will intercept any AJAX requests with the '/Contact/List' endpoint and will use the template passed to $.mockJSON as the response. The template will generate between 50 and 500 contacts each having male first names and having a health ranging from 0 to 100. Each contact will have a random email, birthday, and married boolean field. You can find out more information as to what $.mockJSON supports and how you can extend it from their website.

The following JSON snippet is an example of what the above $.mockJSON template will generate. The above template would generate between 50 to 500 contacts, but for brevity I just included 4.

“contacts”: [{
“married”: false,
“email”: “”,
“firstName”: “Paul”,
“lastName”: “Martinez”,
“birthday”: “12/16/2005”,
“percentHealth”: 37},
“married”: false,
“email”: “”,
“firstName”: “Daniel”,
“lastName”: “Gonzalez”,
“birthday”: “07/11/1997”,
“percentHealth”: 1},
“married”: true,
“email”: “”,
“firstName”: “David”,
“lastName”: “Lewis”,
“birthday”: “04/13/2007”,
“percentHealth”: 62},
“married”: true,
“email”: “”,
“firstName”: “Richard”,
“lastName”: “Rodriguez”,
“birthday”: “05/10/2007”,
“percentHealth”: 6}]

//A bunch more…

</pre>Now, since we have some data coming back from our AJAX request, we can run our code again and proceed to get our front-end working as intended.

View Demo Edit Demo

If you enjoyed this post, please consider sharing it with others via the following Twitter or Reddit buttons. I also have a YouTube Channel with free web development videos that you are welcome to watch and/or subscribe. As always, you can reach out to me on Twitter at @elijahmanor. Thanks and have a blessed day!