AngularJS $timeout work differently

Question

I am trying to run loop with angular $timeout. Here is the thing: When I try to use this $timeout usage. I get nearly 15 requests per second instead of planned 1 per 2 second:

$timeout($scope.checkChallengeAnswerd(challengeTarget), 2000);

But everything is OK if I do something like that:

$timeout(function() { $scope.checkChallengeAnswerd(challengeTarget); }, 2000);

Could anybody explain why does this happen, please?

Here is full function code block:

    $scope.checkChallengeAnswerd = function (challengeTarget) {

     $http({
        method: 'post',
        url: CHESS_URL + "/challenge/check_answerd/",
        headers: {'Content-Type': 'application/x-www-form-urlencoded'},
        transformRequest: function(obj) {
            var str = [];
            for(var p in obj)
            str.push(encodeURIComponent(p) + "=" + encodeURIComponent(obj[p]));
            return str.join("&");
            },
        data: { "target":challengeTarget }
         }).success(function (data, status, headers, config) {

            $scope.answerd = data.answerd;

            if ($scope.answerd == "wait") {
                //alert("wait");
                $timeout(function() { $scope.checkChallengeAnswerd(challengeTarget); }, 2000);
            }else{
               $("div.b111").hide();
               alert($scope.answerd);
            };
         });
};

Answer 1

$timeout service takes first parameter as function and second parameter the number of milliseconds to wait to execute that function.

When you use $timeout($scope.checkChallengeAnswerd(challengeTarget), 2000), you are not passing the function into the $timeout service, instead you are passing the return value of the function.

Using $timeout(function() { $scope.checkChallengeAnswerd(challengeTarget); }, 2000) works fine as you are passing in function to $timeout service.

Other option is to modify the $scope.checkChallengeAnswerd(challengeTarget) function expression as:

$scope.checkChallengeAnswerd = function (challengeTarget) {
    return function () {
        $http({
            method: 'post',
            url: CHESS_URL + "/challenge/check_answerd/",
            headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
            transformRequest: function (obj) {
                var str = [];
                for (var p in obj)
                    str.push(encodeURIComponent(p) + "=" + encodeURIComponent(obj[p]));
                return str.join("&");
            },
            data: { "target": challengeTarget }
        }).success(function (data, status, headers, config) {

            $scope.answerd = data.answerd;

            if ($scope.answerd == "wait") {
                //alert("wait");
                $timeout(function () { $scope.checkChallengeAnswerd(challengeTarget); }, 2000);
            } else {
                $("div.b111").hide();
                alert($scope.answerd);
            };
        });
    };
};