Question

我在函数中有一个函数，但我无法通过变量。我正在使用jQuery和Parse.com 这是我的代码：

 <script>
    $(document).ready(function () {
        var tokfile;
        Parse.initialize(myApp, myID);
        var some_file = Parse.Object.extend("myApp");
        var query = new Parse.Query(some_file);
        query.equalTo("objectId", "xcxcxcxc");

        query.find
        ({
            success: function (results) {
                for (var i = 0; i < results.length; i++) {
                    var object = results[i];
                    console.log(object.id + ' - ' + object.get('some_file'));
                    var myObject = object.get('some_file');
                    var myFile = myObject._url

                }

            },
            error: function (error) {
                alert("Error: " + error.code + " " + error.message);
            }


        });
        $("#mp3").attr("src", myFile)

    });
</script>

<audio controls preload="none" style="width:480px;">
    <source id="mp3" src="placeholder" type="audio/mp3" />

正如您可能看到的那样，我正在尝试将#mp3 id＆＃s; src更改为我从Parse.com获取的URL 现在由于某种原因我只是无法加载它，而DOM则加载了占位符。提前谢谢！

Answer 1

变量的范围是什么，所以将myFile变量放在请求范围之外：

            <script>
        $(document).ready(function () {
            var tokfile;
            Parse.initialize(myApp, myID);
            var some_file = Parse.Object.extend("myApp");
            var query = new Parse.Query(some_file);
            var myFile;
            query.equalTo("objectId", "xcxcxcxc");

            query.find
            ({
                success: function (results) {
                    for (var i = 0; i < results.length; i++) {
                        var object = results[i];
                        console.log(object.id + ' - ' + object.get('some_file'));
                        var myObject = object.get('some_file');
                        var audioElement = document.querySelector('#audioplayer');
                        var source = document.querySelector('#mp3');
                        source.src = myObject._url;
                        audioElement.load();
                    }

                },
                error: function (error) {
                    alert("Error: " + error.code + " " + error.message);
                }


            });
            $("#mp3").attr("src", myFile)

        });
    </script>

    <audio controls preload="none" id="audioplayer" style="width:480px;">
        <source id="mp3" src="placeholder" type="audio/mp3" />

Answer 2

修复变量范围没有帮助，您尝试在值存在之前使用该值。

query.find调用是异步的，因此使用该变量的代码将在将值赋给变量的代码之前运行。

使用回调函数中的值：

    query.find
    ({
        success: function (results) {
            for (var i = 0; i < results.length; i++) {
                var object = results[i];
                console.log(object.id + ' - ' + object.get('some_file'));
                var myObject = object.get('some_file');
                var myFile = myObject._url
                $("#mp3").attr("src", myFile) 
           }
        },
        error: function (error) {
            alert("Error: " + error.code + " " + error.message);
        }
    });

无法在两个嵌套函数之间共享变量

2 个答案: