Javascript:为啥不能在回调函数中获取变量?
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【中文标题】Javascript:为啥不能在回调函数中获取变量?【英文标题】:Javascript: Why can not get variable in callback function?Javascript:为什么不能在回调函数中获取变量? 【发布时间】:2018-10-18 06:40:33 【问题描述】:我已经阅读了几个不同的callback
函数文档,但不幸的是无法成功获得相关的variable
。我在这里缺少什么?
checkNo: function (callback)
var comboQuery = Ext.ComponentQuery.query('[name=foocombo]')[0].getSelectedRecord();
var chkno = comboQuery.get('mychkno'); //Success to get this integer value
callback(chkno); //Error raises here. Debugger says "callback is not a function"
//if (callback) callback(chkno); //I've tried to check callback but did not work as well.
,
setFooCombo: function ()
var me = this;
var fooStore = Ext.getStore('fooComboStore');
var chkno = ''; //Trying to pass an empty value. Not sure if correct approach
var checkno = me.checkNo(chkno); //Trying to get returned value from above function to be able using on url.
fooStore.getProxy().setUrl(MyApp.Url() + '/foo/list?=' + checkno); //I need pass value that return from callback to here
if (typeof checkno === MyApp.NUMBER)
fooStore.load();
// I've tried another way to set new URL as below but did not work too.
// me.checkNo(function (checkno)
//fooStore.getProxy().setUrl(MyApp.Url() + '/foo/list?=' + checkno);
// if (typeof checkno === MyApp.NUMBER)
// fooStore.load();
//
// );
,
更新:在 Rahul Khandelwal 的回答重构了函数之后,当然现在可以工作了。
checkNo: function ()
var comboQuery = Ext.ComponentQuery.query('[name=foocombo]')[0].getSelectedRecord();
var chkno = comboQuery.get('checkno');
return chkno;
,
setFooCombo: function ()
var me = this;
var fooStore = Ext.getStore('fooComboStore');
var checkno = me.checkNo();
fooStore.getProxy().setUrl(MyApp.Url() + '/foo/list?=' + checkno);
if (typeof checkno === MyApp.NUMBER)
fooStore.load();
,
【问题讨论】:
你没有传递函数。 另外,chkno
定义在 setFooCombo
而不是 checkNo
- 它不是函数,因此 callback
不是函数'
因为 checkNo
似乎充满了 syncrhonous 代码,反正你不需要回调
【参考方案1】:
在调用函数时,您没有使用回调功能。将其更改为正常的函数定义,如下所示。
CheckNo: function ()
var comboQuery = Ext.ComponentQuery.query('[name=foocombo]')[0].getSelectedRecord();
var chkno = comboQuery.get('mychkno'); //Success to get this integer value
return chkno; //Error raises here. Debugger says "callback is not a function"
//if (callback) callback(chkno); //I've tried to check callback but did not work as well.
要了解回调的工作原理,请使用以下链接:
This *** question
【讨论】:
【参考方案2】:me.checkNo(function() return checkNo;)
【讨论】:
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