nodejs中的变量作用域误解
Variable Scope in nodejs misunderstanding
我很难理解为什么从另一个函数返回一个数组只局限于一个代码块。即:
exports.join = function(req, res){
User.findById(req.user._id, function(err, user) {
var dupe = []; //placeholder array
var arr = user.forms_container.joinList;
var title = user.forms_container.title;
arr.forEach(function (rep) {
//console.log(rep);
Report.findById(rep).deepPopulate('subreport.subreport.subreport.subreport.subreport.subreport').execAsync()
.then(function(doc) {
//console.log(doc);
dupe.push(doc);
treeCycle(doc, dupe);
console.log(dupe);
}).catch(function(err) {
throw err;
});
tracker = tracker + 1;
if(tracker == arr.length) {
console.log(dupe); //returns [];
var counter = 0;
var masterbody;
for(var x = 0; x < dupe.length; x++) {
masterbody = masterbody + dupe[x].body;
counter = counter + 1;
}
if(counter==dupe.length) {
newDoc.body = masterbody;
//newDoc.save();
res.json(newDoc);
}
}
});
});
};
一次，我调用treeCycle，它将迭代该函数(递归函数)并开始填充数组"dupe"，如果我在控制台中记录它，它显示它已经完成，这是控制台c/p'd:
[ { _id: 55c35cd942dd12ec19b30f2e,
owner: 55a80b8404dc0dc8187395d8,
title: 'Chrome1',
date: 'Thu Aug 06 2015 09:10:49 GMT-0400 (Eastern Daylight Time)',
body: '123213',
__v: 0,
isCompleted: false,
subreport: [],
authors: [ 'Karan Kotwal' ],
author: [ 55a80b8404dc0dc8187395d8 ] } ]
[ { _id: 55c35cd942dd12ec19b30f2e,
owner: 55a80b8404dc0dc8187395d8,
title: 'Chrome1',
date: 'Thu Aug 06 2015 09:10:49 GMT-0400 (Eastern Daylight Time)',
body: '123213',
__v: 0,
isCompleted: false,
subreport: [],
authors: [ 'Karan Kotwal' ],
author: [ 55a80b8404dc0dc8187395d8 ] },
{ _id: 55c8d774e904bc141681e115,
body: 'dddd',
owner: 55a80b8404dc0dc8187395d8,
date: 'Mon Aug 10 2015 12:55:16 GMT-0400 (Eastern Daylight Time)',
title: 'herdrute',
__v: 1,
isCompleted: false,
subreport: [],
authors: [ 'Karan Kotwal' ],
author: [ 55a80b8404dc0dc8187395d8 ] } ]
[ { _id: 55c35cd942dd12ec19b30f2e,
owner: 55a80b8404dc0dc8187395d8,
title: 'Chrome1',
date: 'Thu Aug 06 2015 09:10:49 GMT-0400 (Eastern Daylight Time)',
body: '123213',
__v: 0,
isCompleted: false,
subreport: [],
authors: [ 'Karan Kotwal' ],
author: [ 55a80b8404dc0dc8187395d8 ] },
{ _id: 55c8d774e904bc141681e115,
body: 'dddd',
owner: 55a80b8404dc0dc8187395d8,
date: 'Mon Aug 10 2015 12:55:16 GMT-0400 (Eastern Daylight Time)',
title: 'herdrute',
__v: 1,
isCompleted: false,
subreport: [],
authors: [ 'Karan Kotwal' ],
author: [ 55a80b8404dc0dc8187395d8 ] },
{ _id: 55bf7465c60c959015dee0ed,
owner: 55a80b8404dc0dc8187395d8,
title: 'ffefeeffefeeffefefe',
date: 'Mon Aug 03 2015 10:02:13 GMT-0400 (Eastern Daylight Time)',
body: 'efefefefef',
__v: 0,
isCompleted: false,
subreport: [],
authors: [ 'Karan Kotwal' ],
author: [ 55a80b8404dc0dc8187395d8 ] } ]
[ { _id: 55c35cd942dd12ec19b30f2e,
owner: 55a80b8404dc0dc8187395d8,
title: 'Chrome1',
date: 'Thu Aug 06 2015 09:10:49 GMT-0400 (Eastern Daylight Time)',
body: '123213',
__v: 0,
isCompleted: false,
subreport: [],
authors: [ 'Karan Kotwal' ],
author: [ 55a80b8404dc0dc8187395d8 ] },
{ _id: 55c8d774e904bc141681e115,
body: 'dddd',
owner: 55a80b8404dc0dc8187395d8,
date: 'Mon Aug 10 2015 12:55:16 GMT-0400 (Eastern Daylight Time)',
title: 'herdrute',
__v: 1,
isCompleted: false,
subreport: [],
authors: [ 'Karan Kotwal' ],
author: [ 55a80b8404dc0dc8187395d8 ] },
{ _id: 55bf7465c60c959015dee0ed,
owner: 55a80b8404dc0dc8187395d8,
title: 'ffefeeffefeeffefefe',
date: 'Mon Aug 03 2015 10:02:13 GMT-0400 (Eastern Daylight Time)',
body: 'efefefefef',
__v: 0,
isCompleted: false,
subreport: [],
authors: [ 'Karan Kotwal' ],
author: [ 55a80b8404dc0dc8187395d8 ] },
{ _id: 55c361705d00464419a1d40c,
owner: 55a80b8404dc0dc8187395d8,
title: 'IE11',
date: 'Thu Aug 06 2015 09:30:24 GMT-0400 (Eastern Daylight Time)',
body: 'PEWPEWPEWPW',
__v: 1,
isCompleted: false,
subreport:
[ { _id: 55ca4d5456f8cdb416d36092,
body: 'testest',
owner: 55a80b8404dc0dc8187395d8,
date: 'Tue Aug 11 2015 15:30:28 GMT-0400 (Eastern Daylight Time)',
title: 'Sub1',
__v: 2,
parentReport: 55c361705d00464419a1d40c,
isCompleted: false,
subreport: [Object],
authors: [Object],
author: [Object] } ],
authors: [ 'Karan Kotwal' ],
author: [ 55a80b8404dc0dc8187395d8 ] },
{ _id: 55ca4d5456f8cdb416d36092,
body: 'testest',
owner: 55a80b8404dc0dc8187395d8,
date: 'Tue Aug 11 2015 15:30:28 GMT-0400 (Eastern Daylight Time)',
title: 'Sub1',
__v: 2,
parentReport: 55c361705d00464419a1d40c,
isCompleted: false,
subreport:
[ { _id: 55ca53728ecc9400150610b6,
body: 'sadsadasdasdasdadasdsadasdasEnter subreport here',
owner: 55a80b8404dc0dc8187395d8,
date: 'Tue Aug 11 2015 15:56:34 GMT-0400 (Eastern Daylight Time)',
title: 'Sub1''s sub1',
__v: 1,
parentReport: 55ca4d5456f8cdb416d36092,
isCompleted: false,
subreport: [],
authors: [Object],
author: [Object] } ],
authors: [ 'Jeff The man' ],
author: [ 55ad14bac2419660021d80b0 ] },
{ _id: 55ca53728ecc9400150610b6,
body: 'sadsadasdasdasdadasdsadasdasEnter subreport here',
owner: 55a80b8404dc0dc8187395d8,
date: 'Tue Aug 11 2015 15:56:34 GMT-0400 (Eastern Daylight Time)',
title: 'Sub1''s sub1',
__v: 1,
parentReport: 55ca4d5456f8cdb416d36092,
isCompleted: false,
subreport: [],
authors: [ 'Empty Empty' ],
author: [ 55bbbc20877f48a01bf0c8d9 ] } ]
但是这样做，调用数组dupe的最终版本的控制台将返回空。我在块if(tracker == array.length);中这样做，我认为它的作用域将贯穿整个函数，因为我在开始时初始化了它。
TreeCycle:
function treeCycle(doc, arr) {
if(doc.subreport.length != 0) {
for (var x = 0; x < doc.subreport.length; x++){
arr.push(doc.subreport[x]);
//console.log(arr);
if(doc.subreport[x].subreport.length != 0) {
treeCycle(doc.subreport[x], arr);
}
}
}
else {
return arr;
}
};
这似乎是一个异步问题，您的if(tracker == arr.length) {部分在树周期之前运行。当你的异步任务完成后，你需要调用你的if(tracker == arr.length) {部分。
的例子:
exports.join = function(req, res) {
User.findById(req.user._id, function(err, user) {
var dupe = []; //placeholder array
var arr = user.forms_container.joinList;
var title = user.forms_container.title;
arr.forEach(function(rep) {
//console.log(rep);
Report.findById(rep).deepPopulate('subreport.subreport.subreport.subreport.subreport.subreport').execAsync()
.then(function(doc) {
//console.log(doc);
dupe.push(doc);
treeCycle(doc, dupe);
console.log(dupe);
tracker = tracker + 1;
if (tracker == arr.length) {
console.log(dupe); //returns [];
var counter = 0;
var masterbody;
for (var x = 0; x < dupe.length; x++) {
masterbody = masterbody + dupe[x].body;
counter = counter + 1;
}
if (counter == dupe.length) {
newDoc.body = masterbody;
//newDoc.save();
res.json(newDoc);
}
}
}).catch(function(err) {
throw err;
});
});
});
};
这很可能是你如何使用承诺的问题。我建议你仔细阅读它们，看看它们是如何工作的，以及你应该如何重构你的代码来更好地使用它们。
如果您将if (tracker...块移动到.then(回调(或另一个.then)，它可能会工作。
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