how to prevent duplicated $http requests in AngularJS app?

Lets say you have $http in your controller.js file.

Many request to server

$http.get('/link/to/file.php');

Just one request to server, no matter how many times you will call this method:

$http.get('/link/to/file.php', {cache: true});

Example:

(function() {
    'use strict';

    angular
            .module('yourModuleName')
            .controller('DashboardCtrl', DashboardCtrl);

    DashboardCtrl.$inject = ['$scope'];

    function DashboardCtrl($scope) {

       $scope.get = function () {
           $http.get('/link/to/file.php', {cache: true}).then(function(response) {
               // it will do GET request just once
               // later you will get the same response from cacheFactory
           })
       }
    }

}());

I would like to complement @VikasChauhan answer, however I do not have enough reputation to comment on his answer.

His code works great for me, except the part where he returns null. That causes Angular to throw a bunch of errors all over.

Instead of null, I simply reject the request:

return $q.reject(request);

Here's my function:

$httpProvider.interceptors.push(['$injector', '$q', function interceptors($injector, $q) {
    return {
        // preventing duplicate requests
        request: function request(config) {
            var $http = $injector.get('$http');
            var _config = angular.copy(config);
            delete _config.headers;

            function isConfigEqual(pendingRequestConfig) {
                var _pendingRequestConfig = angular.copy(pendingRequestConfig);
                delete _pendingRequestConfig.headers;

                return angular.equals(_config, _pendingRequestConfig);
            }

            if ($http.pendingRequests.some(isConfigEqual)) {
                return $q.reject(request);
            }

            return config;
        }
    };
}
]);

Hope this helps other people.

You can create a function to cancel the first http request, when calling the another one on the button click. Here is a reference that uses $q.defer() function that helped me on a similar issue: http://odetocode.com/blogs/scott/archive/2014/04/24/canceling-http-requests-in-angularjs.aspx

In my project, i was facing this problem. I found a very useful working solution here

And implemented it inside the config:

function config($routeProvider, $httpProvider) {

    $httpProvider.interceptors.push(['$injector', function interceptors($injector) {
        // Manually injecting dependencies to avoid circular dependency problem
        return {
            // preventing duplicate requests
            'request': function request(config) {
                var $http = $injector.get('$http'),
                copiedConfig = angular.copy(config);

                delete copiedConfig.headers;
                function configsAreEqual(pendingRequestConfig) {
                    var copiedPendingRequestConfig = angular.copy(pendingRequestConfig);

                    delete copiedPendingRequestConfig.headers;

                    return angular.equals(copiedConfig, copiedPendingRequestConfig);
                }

                if ($http.pendingRequests.some(configsAreEqual)) {
                    debugger;
                    return null;
                }

                return config;
            }
        }
    }
    ]);
}