10-angular.identity

函数返回本身的第一个参数。这个函数一般用于函数风格。

格式：angular.identity()

<!DOCTYPE html>
<html ng-app="Demo">
<head>
    <meta charset="UTF-8">
    <title></title>
    <script src="framework/angular.js"></script>
    <script type="text/javascript">
        (function () {
            angular.module("Demo", [])
                    .controller("testCtrl", function testCtrl() {
                        var getResult = function (fn, val) {
                            return (fn || angular.identity)(val);
                            //angular.identity(val) == fn(val)
                        };
                        var result = getResult(function (n) { return n * 2; }, 3); //  result = 6
                        var null_result = getResult(null, 3);//  null_result = 3
                        var undefined_result = getResult(undefined, 3);// undefined _result = 3
            });
        }())
    </script>
</head>
<body>
<div ng-controller="testCtrl">
</div>
</body>
</html>