title: Check duplicate using ko.observableArray
body: <p>How can I check the duplicate signatures before adding. In the below scenario, I wanted add signature if no signature found the list.</p>
  
  <pre><code>    var Signature = function (name, interestDeclared) {
          this.Name = ko.observable(name);
         this.RelevantInterest = ko.observable(interestDeclared);
      } 
  
     viewModel = {
  
      signatures: ko.observableArray([]),
  
      addSignature: function () {
          var name = $('#signatureName').val();
          var intd = $('#interest').is(':checked');
  
          this.signatures.push(new Signature(name, intd));
  
      },
      deleteSignature: function (signature) {
          this.signatures.remove(signature);
       },
  
      insertWitness: function (signature, position) {
          this.signatures.splice(position, 0, signature);
        }
  };
  
  ko.applyBindings(viewModel, document.getElementById("signatories"));
  </code></pre>
  
  <p>Thanks,
  -Naren</p>