如何让函数直接调用自身？

Question

I have this function which I define and as soon as it is defined I execute it. Is there a way I can combine the definition and the execution in one go as this is the only place this function is used?

    $scope.examWatchCollection = function () {
        $scope.$watchCollection('[config.examStatusId, config.examTypeId]',
            function (newValue, oldValue) {
                if (_o.checkWatch(newValue, oldValue)) {
                    _u.putConfigs($scope.config);
                    $scope.grid.backup = [];
                    $scope.grid.data = [];
                }
            });
    };

    $scope.examWatchCollection();

Answer 1

You are over complicating the problem. Simply, don't create a function at all.

$scope.$watchCollection('[config.examStatusId, config.examTypeId]',
    function(newValue, oldValue) {
        if (_o.checkWatch(newValue, oldValue)) {
            _u.putConfigs($scope.config);
            $scope.grid.backup = [];
            $scope.grid.data = [];
        }
    });

If you still want a function, you can make that an IIFE like this

(function() {
    $scope.$watchCollection('[config.examStatusId, config.examTypeId]',
        function(newValue, oldValue) {
            if (_o.checkWatch(newValue, oldValue)) {
                _u.putConfigs($scope.config);
                $scope.grid.backup = [];
                $scope.grid.data = [];
            }
        });
}());

The second version, creates a function object and then invoke it immediately. Normally, this is used to limit the scope of the variables used by the piece of code, as we don't have block scope in JavaScript. But I strongly believe you should go with the first option.

Answer 2

(function () {
    $scope.$watchCollection('[config.examStatusId, config.examTypeId]',
            function (newValue, oldValue) {
                if (_o.checkWatch(newValue, oldValue)) {
                    _u.putConfigs($scope.config);
                    $scope.grid.backup = [];
                    $scope.grid.data = [];
                }
    });
})();

Answer 3

If you never otherwise use it, then you don't need to retain a reference to it. Just define it anonymously and execute it right away:

(function () {
    $scope.$watchCollection('[config.examStatusId, config.examTypeId]',
        function (newValue, oldValue) {
            if (_o.checkWatch(newValue, oldValue)) {
                _u.putConfigs($scope.config);
                $scope.grid.backup = [];
                $scope.grid.data = [];
            }
        });
}());

In JavaScript a function is an object like any other object. You can execute it from its name or from the definition of the function itself. Any function, whether referenced by name or defined in-line, will execute if there are parentheses after it.

It might even be simpler to not create a function at all and just, well, execute the code:

$scope.$watchCollection('[config.examStatusId, config.examTypeId]',
    function (newValue, oldValue) {
        if (_o.checkWatch(newValue, oldValue)) {
            _u.putConfigs($scope.config);
            $scope.grid.backup = [];
            $scope.grid.data = [];
        }
    });