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Editorial Team
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Asked: 2026-05-25T19:27:57+00:00

I’m still learning the proper usage of Knockout and I’ve found myself quickly getting

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I’m still learning the proper usage of Knockout and I’ve found myself quickly getting away from ever typing ko.observable when setting up my viewmodel and instead just defining an object literal and passing it through the mapping plugin with something like 

var viewModel = ko.mapping.fromJS(data);

or at the very least, something along the lines of stuffing all of my data into an attribute on the viewModel like so

var viewModel = { 
    ... events etc ... , 
    "data": ko.mapping.fromJS(data)
}

To be honest, the main reason I’ve been doing this is to get around having to type ko.observable and ko.observableArray repetitively. I’m just trying to figure out if this is a good approach and if there are any downsides to dropping the specific var x = ko.observable() declaration all together. Also, I’m doing this all on load, not in response to any ajax call etc, which from what I can tell, is what the mapping plugin was designed for.

In your work with knockout, do you still declare the observables manually, one by one, or have you gone with the mapping.fromJS method that I use? Are there any specific downsides to using the mapping plugin so frequently like this?

Edit:

Specific Example

In this article, Steve sets up his viewModel by doing

var initialData = [ { ... } , { ... } ]; // json from the serializer
var viewModel = {
    gifts : ko.observableArray(initialData)
};

Normally, I’d just use ko.mapping.fromJS for this situation as well, specifically to make sure the objects within the array are turned into observables as well. Looking at what he did, my approach seems like its overkill and adds a bit of unnecessary overhead.

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1 Answer

  1. Editorial Team

    My suggestion to you would the same another questioned I just answered at https://stackoverflow.com/questions/7499133/mapping-deeply-hierarchical-objects-to-custom-classes-using-knockout-mapping-plug.

    Your reasoning for using mapping plug-in is reasonable and the one that I use. Why type more code than you have to?

    In my experience with knockout (all of 4 months), I’ve found that the less I do manually and let the knockout routines do their thing, the better my apps seem to run. My suggestion is try the simplest approach first. If it doesn’t meet your needs, look at how the simple approach is doing it’s “thing” and determine what has to change to meet your needs.

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