Spreadsheet-like formulas on the DOM

Question

I am looking for a way to dynamically bind formulas throughout my DOM.

We have a data intensive app, and currently I write many handlers to try and recalculate and updat

Answer 1

Have a look at jQuery Calculation Plug-in. But I'm not sure whether you can define any formula

Answer 2

What you are describing sounds a lot like "Bindings" and "Computed Properties" from Sproutcore or Ember.js.

Answer 3

You can use knockout.js to get the functionality you're looking for.

Knockout.js implements an mvvm pattern in your javascript. Here is how they define MVVM:

MVVM and View Models Model-View-View Model (MVVM) is a design pattern for building user interfaces. It describes how you can keep a potentially sophisticated UI simple by splitting it into three parts:

A model: your application’s stored data. This data represents objects and operations in your business domain (e.g., bank accounts that can perform money transfers) and is independent of any UI. When using KO, you will usually make Ajax calls to some server-side code to read and write this stored model data.

A view model: a pure-code representation of the data and operations on a UI. For example, if you’re implementing a list editor, your view model would be an object holding a list of items, and exposing methods to add and remove items.

Note that this is not the UI itself: it doesn’t have any concept of buttons or display styles. It’s not the persisted data model either - it holds the unsaved data the user is working with. When using KO, your view models are pure JavaScript objects that hold no knowledge of HTML. Keeping the view model abstract in this way lets it stay simple, so you can manage more sophisticated behaviors without getting lost.

A view: a visible, interactive UI representing the state of the view model. It displays information from the view model, sends commands to the view model (e.g., when the user clicks buttons), and updates whenever the state of the view model changes.

When using KO, your view is simply your HTML document with declarative bindings to link it to the view model. Alternatively, you can use templates that generate HTML using data from your view model.

So you'll create your "model" which includes the data in the spreadsheet, along with any functions you need to recalculate data. Then you'll have your view, which automatically updates (aka recalculates) the data as the user changes things on the page.

http://knockoutjs.com

Answer 4

You can approach the problem like this:

• by storing the vars on the DOM node you want to keep update via $('myDomElement').data('varX',data);
• by overloading the setData-method for that DOM node via $("myDomElement").bind("setData", function(key,value){ setTimeout(function() { $("myDomElement").trigger("formula"); },10); return value; });
• and by finally creating your update formula like $('myDomElement').bind("formula",function() { this.html(foo()); });

Woehoe, I reread your post and found you don't really specify you have vars in which you store the data ... instead you got cells ...

• in this case you could just add a changeHandler to the cells that update the formula ..

hmmm, actually, I think I forgot what the problem was, it seems a bit too obvious what I'm supposing here ... sorry if of no help

anyway ... I did a quick google on data binding jquery, that's where I found you can bind the setData/getData-events on $.data: What you might not know about jquery

I also found this, which might or not be of interest to your spreadsheety-approach: using jquery.data to detect form changes

What's more, I agree with previous answers, you could always use a framework -- personally I prefer jsmvc

Answer 5

You're going to want a framework like Backbone.js or Knockout

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Backbone.js

http://documentcloud.github.com/backbone/

Cited from Backbone: With Backbone, you represent your data as Models, which can be created, validated, destroyed, and saved to the server. Whenever a UI action causes an attribute of a model to change, the model triggers a "change" event; all the Views that display the model's state can be notified of the change, so that they are able to respond accordingly, re-rendering themselves with the new information. In a finished Backbone app, you don't have to write the glue code that looks into the DOM to find an element with a specific id, and update the HTML manually — when the model changes, the views simply update themselves.

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Knockout.js

http://www.knockoutjs.com/

Cited from Knockout JS: By encapsulating data and behavior into a view model, you get a clean, extensible foundation on which to build sophisticated UIs without getting lost in a tangle of event handlers and manual DOM updates.

Answer 6

I just develop plugin that parse formula, using jison parser in its core, currently the formula is still limited to sum, avg, min and max, but will add more function as requested.

http://xsanisty.com/calx/