gistfile1.js

angular.module('todoApp', [])...
.controller....

.filter('searchFilter', function() {
  return function(input, searchText) {
    if(typeof searchText === 'undefined' || searchText == '')return input;
    var output = [];
    for(var i=0;i<input.length;i++){
      if(input[i].text.indexOf(searchText) > -1){
        output.push(input[i]);
      }
    }
    return output;
  };
});