javascript - jQuery DOM manipulation from Knockout ViewModel - use bindingHandlers? -

i've got knockout viewmodel looks this:

function myviewmodel() {     this.update = function() {         ...     }     ... } 

and bindinghandler looks this:

ko.bindinghandlers.mybindinghandler = {     init: function(element, valueaccessor, allbindings, viewmodel) {         function manipulatedom(element) {             ...         }     } } 

i want myviewmodel call manipulatedom whenever update method called.

i using callback set in bindinghandler:

function myviewmodel() {     this.update = function() {         ...         this.mybindinghandlercallback();     }     ... }  ko.bindinghandlers.mybindinghandler = {     init: function(element, valueaccessor, allbindings, viewmodel) {         viewmodel.mybindinghandlercallback = manipulatedom.bind(null, element);     } }  <div data-bind="mybindinghandler: null"></div> 

another idea had use 'updatecount' observable , subscribing in bindinghandler:

function myviewmodel() {     this.updatecount = ko.observable(0);     this.update = function() {         ...         this.updatecount(this.updatecount() + 1);     }     ... }  ko.bindinghandlers.mybindinghandler = {     update: function(element) {         manipulatedom(element);     } }  <div data-bind="mybindinghandler: updatecount"></div> 

both of these solutions feel fragile , messy. 'knockout' way of approaching sort of problem? should manipulating dom within viewmodel?

i should add manipulatedom function has lot of logic isn't applicable in knockout fashion (measuring window heights, measuring div heights etc...)

thanks!

second approach (with counter) better, because viewmodel shouldn't override , change viewmodel's behavior overriding properties.

instead of having counter, if update method changes other observable properties create computed property subscribe current state of viewmodel , automatically invoke dom manipulation binding if pass binding parameter, no need increment counter or other flag then.