title: KnockoutJs - Pushing to an element in an observable array does not work
body: <p>I have an object (analysisLogData) that I use to generate a table using KnockoutJS. Here's the viewModel containing this object:</p>
  
  <pre><code>function AppViewModel() {
      var self = this;
      self.analysisLogData = ko.observableArray();
      self.analysisLogTitle = ko.observable("Warnings")
  
      self.changeAnalysisLog = function(title) {
           self.analysisLogTitle(title)   
      }
  
      var data =
  
      {
          "Warnings": [
              {
                  "number": 3002,
                      "description": "There may be a problem with the device you are using if you use the default profile"
              },
  
              {
                  "number": 3001,
                      "description": "There may be a problem with the device you are using if you don't use the default profile"
              }
  
              ]
  
          ,
              "Errors": [
              {
  
  
                  "number": 1000,
                      "description": "No networks are loaded"
              },
  
              {
                  "number": 1002,
                      "description": "No devices are loaded"
              }]
  
  
  
  
      }
  
  
      self.addLog = function (type, content) {
          self.analysisLogData()[type].push(content);
      }
  
      self.analysisLogData.push(data)
  
  
  }
  
  ko.applyBindings(new AppViewModel());
  </code></pre>
  
  <p>You can see the result here in a JSFiddle: <a href="http://jsfiddle.net/etiennenoel/V4r2e/5/" rel="nofollow">http://jsfiddle.net/etiennenoel/V4r2e/5/</a></p>
  
  <p>I want to be able to add an error or a warning without losing the warnings or errors already present.</p>
  
  <p>I tried to do the following in the <code>self.addLog</code> function: </p>
  
  <pre><code>self.addLog = function (type, content) {
          self.analysisLogData()[type].push(content);
      } 
  </code></pre>
  
  <p>but it says that it can't push to an undefined object...</p>