Question

Question about JS Knockout library – I have three inputs, all data-Bind-ed to the same variable. Two have a boolean value of false and one has a boolean value of true. (I can’t change them to ints, unfortunately, which would make this problem easier). Although the two false-valued inputs share behavior, I need to differentiate between them somehow to trigger slightly different behaviors.

Is it possible to data-bind each to another variable, with different values? So instead of each being

    <input data-Bind="checked:test" value="false">

I would have something like

    <input data-Bind="test, test2" value="false, 1">

and

    <input data-Bind="test, test2" value="false, 2">?

I tried that directly and didn’t work so I don’t know if it’s possible. Thanks so much.

Answer 1

You cant bind multiple variables directly but creating a custom bind function do the trick for you.

Example : http://jsfiddle.net/gurkavcu/ePW8Y/
** Change input value (true , false) to trigger the update function

HTML

<input data-bind="customData: test , v1 : test2"/>
<div>
    <span data-bind ="text : test"/>
</div>
<div>
    <span data-bind ="text : test2"/>
</div>

JS

ko.bindingHandlers.customData = {
      init: function(element, valueAccessor, allBindingsAccessor, viewModel) {  
           $(element).change(function () {
                valueAccessor()(element.value);
            });       
      },
       update: function(element, valueAccessor, allBindingsAccessor, viewModel) {
          var value =ko.utils.unwrapObservable(valueAccessor());
          var v1 = allBindingsAccessor().v1;

          if(value === "true") {
             v1("1"); 
             console.log(v1());
          }
          else  if(value === "false") {
             v1("2"); 
             console.log(v1());
          }
     }
};  


function ViewModel() {

    this.test =  ko.observable(false);
    this.test2 =  ko.observable("2");

};

$(function() {  

    var viewModel = new ViewModel();
    ko.applyBindings(viewModel); 

})​

Modify the update function for your needs. You can add any number of variable to the binding with v1 : … , v2 : … , v3 : … and access it via allBindingsAccessor().v1 , allBindingsAccessor().v2 , allBindingsAccessor().v3