[英]NodeJS, Mongoose, return variable
預先感謝您的時間和答復:
我一直在嘗試做一些“應該”容易的事情,但是這讓我發瘋了。
目的是將函數的結果分配給一個變量,我以后可以在POST上使用該變量將信息發送到我的MongoDB。
我有一個文檔如下的模型:
{ "__v" : 0, "_id" : ObjectId("54ad1aa637ce5c566c13d18f"), "num" : 9 }
我想要的是捕獲此數字“ num”:9到一個變量。 我創建了一個通過模型查詢mongodb的函數。
function getNum(){
var Num = require('./models/num.js');
var callback = function(){
return function(err, data) {
if(err) {
console.log("error found: " + err);
}
console.log("the number is: " + data.num);
}
};
return Num.findOne({}, callback());
};
然后只是為了測試我將該函數分配給變量,然后嘗試console.log它只是為了測試結果是否良好。
// =====================================
// TESTING ==============================
// =====================================
app.get('/testing',function(req, res, next){
var a = getNum();
console.log(a);
});
我的輸出是:
{ _mongooseOptions: {},
mongooseCollection:
{ collection:
{ db: [Object],
collectionName: 'num',
internalHint: null,
opts: {},
slaveOk: false,
serializeFunctions: false,
raw: false,
pkFactory: [Object],
serverCapabilities: undefined },
opts: { bufferCommands: true, capped: false },
name: 'num',
conn:
{ base: [Object],
collections: [Object],
models: [Object],
config: [Object],
replica: false,
hosts: null,
host: 'localhost',
port: 27017,
user: undefined,
pass: undefined,
name: 'project',
options: [Object],
otherDbs: [],
_readyState: 1,
_closeCalled: false,
_hasOpened: true,
_listening: true,
_events: {},
db: [Object] },
queue: [],
buffer: false },
model:
{ [Function: model]
base:
{ connections: [Object],
plugins: [],
models: [Object],
modelSchemas: [Object],
options: [Object] },
modelName: 'Num',
model: [Function: model],
db:
{ base: [Object],
collections: [Object],
models: [Object],
config: [Object],
replica: false,
hosts: null,
host: 'localhost',
port: 27017,
user: undefined,
pass: undefined,
name: 'project',
options: [Object],
otherDbs: [],
_readyState: 1,
_closeCalled: false,
_hasOpened: true,
_listening: true,
_events: {},
db: [Object] },
discriminators: undefined,
schema:
{ paths: [Object],
subpaths: {},
virtuals: [Object],
nested: {},
inherits: {},
callQueue: [Object],
_indexes: [],
methods: {},
statics: {},
tree: [Object],
_requiredpaths: undefined,
discriminatorMapping: undefined,
_indexedpaths: undefined,
options: [Object],
_events: {} },
options: undefined,
collection:
{ collection: [Object],
opts: [Object],
name: 'num',
conn: [Object],
queue: [],
buffer: false } },
op: 'findOne',
options: {},
_conditions: {},
_fields: undefined,
_update: undefined,
_path: undefined,
_distinct: undefined,
_collection:
{ collection:
{ collection: [Object],
opts: [Object],
name: 'num',
conn: [Object],
queue: [],
buffer: false } },
_castError: null }
**the number is: 9**
這是我在未定義的其他方法中可以獲得的結果之一。
誰能知道我該怎么解決?
再次感謝您的幫助。
您無法返回諸如findOne
之類的異步函數的結果,需要使用回調。
因此,需要將其重寫為:
function getNum(callback){
var Num = require('./models/num.js');
return Num.findOne({}, callback);
};
app.get('/testing',function(req, res, next){
getNum(function(err, a) {
console.log(a);
});
});
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