data.map is not a function

Objects, {} in JavaScript do not have the method .map(). It's only for Arrays, [].

So in order for your code to work change data.map() to data.products.map() since products is an array which you can iterate upon.

The right way to iterate over objects is

Object.keys(someObject).map(function(item)...
Object.keys(someObject).forEach(function(item)...;

// ES way
Object.keys(data).map(item => {...});
Object.keys(data).forEach(item => {...});

Read here for details

In some cases (not in all), the SIMPLEST answer is to put "data" into a pair of square brackets (i.e. [data]) to change the items in the "data" into an array:

     $.getJSON("json/products.json").done(function (data) {

         var allProducts = [data].map(function (item) {
             return new getData(item);
         });

     });

Here, [data] is an array, and the ".map" method can be used on it. It works for me!

Or convert "data" into an array in the following way:

     let dataArr = Array.from(data);

     $.getJSON("json/products.json").done(function (dataArr) {

         var allProducts = dataArr.map(function (item) {
             return new getData(item);
         });

     });

But the very question here is to get the "products" out of the "data":

     data.products

The "products" is an array.

And then ".map" can be used:

     data.products.map

data is not an array, it is an object with an array of products so iterate over data.products

var allProducts = data.products.map(function (item) {
    return new getData(item);
});