Extjs JSON数据存储中的全局变量

我想声明一个全局变量，它从数据存储中获取值，并在警报窗口中显示其值

var params = 1;

var storeTeacher = new Ext.data.JsonStore({
       id: 'IDstoreTeacher',
       url: 'school.php',
       method: 'POST',
       baseParams:{task: "LABEL",
                   parametar: params},
       root: 'rows',
       fields: 
              [{name: 'NameT', type: 'string', mapping: 'Teacher_name'}],
       autoLoad: true   
    });

var TeacherName;

storeTeacher.load({ 
       scope: this, 
       callback: function (records, operation, success) { 
                   TeacherName = storeTeacher.getAt(0).get('NameT');
              }
});


alert(TeacherName);

但是，我得到的唯一一个提示窗口是：未定义的您的

提示（TeacherName）storeTeacher.load执行回调之前，正在执行code>call

如果将
警报（TeacherName）
放入回调函数，它将正确填充您的TeacherName并在警报中正确显示：

storeTeacher.load({
    scope: this,         
    callback: function (records, operation, success) {                     
        TeacherName = storeTeacher.getAt(0).get('NameT');
        alert(TeacherName);   
} }); 

这种行为是意料之中的