Question

Problem

I have played around a lot with the knockoutJS mapping plugin.

My problem can be best shown in the following jsFiddles.

This one works. But this dont work.

I get the the error in the console

Uncaught Error: ko.mapping.updateFromJS, use ko.mapping.fromJS instead. Please note that the order of parameters is different!

Why i get this error and whats the difference in the fiddles ?

My Code

var viewModel = ko.mapping.fromJS({
    "State" : 1,
    "Text" : "Hello"
});

$("button").click(function() 
{
    var response = {
        "State" : 2,
        "Text" : "World"
    }
        
    ko.mapping.updateFromJS(viewModel, response);
});
    
ko.applyBindings(viewModel);

Answer 1

You are using different versions of the ko mapping plugin:

In your working fiddle: http://wiredwestwebdesign.com/knockout.mapping.js

In you not working fiddle: https://raw.github.com/SteveSanderson/knockout.mapping/master/build/output/knockout.mapping-latest.js

And the method in question ko.mapping.updateFromJS was deprecated about a year ago in this changeset: First part of removing the updateFromJS* calls.

And how to fix this error:

Just do what the exception says: use ko.mapping.fromJS and watch for the parameter order:

ko.mapping.fromJS(response, viewModel);

Demo fiddle.