Substring in Angularjs using filters?

Try this one:

HTML

<div ng-controller = "fessCntrl"> 
  <h1>Only path without domain name:</h1>
        <ul>
            <li ng-repeat="url in urls | myCustomFilter">{{url.path}}</li>
        </ul>
</div>

JS

var fessmodule = angular.module('myModule', []);

fessmodule.controller('fessCntrl', function ($scope) {
     $scope.urls = [{
        path: 'http://a.com/index'        
    }, {
         path: 'http://a.com/home'        
    }, {
        path: 'http://a.com/etc'        
    }, {
        path: 'http://a.com/all'        
    }];

    $scope.otherCondition = true;
});
fessmodule.$inject = ['$scope'];

 fessmodule.filter('myCustomFilter', function() {
   return function( urls) {
    var filtered = [];

    angular.forEach(urls, function(url) {
        filtered.push( {path:url.path.substring("http://a.com".length, url.path.length)});
    });

    return filtered;
  };
});

Demo Fiddle

As a side note:

Try to write filters out of controller.

AngularJS v 1.4.5 supports a standard "limitTo" filter for arrays(including string) with parameters length and offset:

<div ng-controller = "SampleController"> 
  <h1>Result of substring equivalent filter:</h1>
        <ul>
            <li ng-repeat="url in urls">{{url.path | limitTo:5:12}}</li>
        </ul>
</div>

Note: This solution fails in case of dynamic domain length("http://a.com" static length of 12).

Note 2: Increase length to the maximum resulting length of path(Max is "index" having length of 5).

Overview of all filters supported by AngularJS out of the box.