[英]Refactoring pattern in javascript
我正在編寫一個小型應用程序並與數據庫進行通信,而不是使用回調模式,而是使用Promises來簡化代碼。 經過大量的編碼,我現在可以在代碼中非常頻繁地看到某種模式,我需要知道如何重構它,以便將類似的邏輯放在一個地方。
var queryString = "select * from users u inner join "+
"(select user_id, count(id) cnt from applications "+
"where id in (select id from applications where "+
"created_at > current_date - interval '1 week') "+
"group by user_id) a on u.id = a.user_id order by a.cnt desc";
var self = this;
return new Promise(function _promise(resolve, reject) {
req.client.query(queryString, [], function result(error, result) {
req.done(error);
if (error) {
console.log('error ' + error.message);
return reject(error);
}
var users = result.rows.map(function(row) {
return new User(row);
});
resolve(users);
});
});
上面的模式是我的每種方法唯一的變化是if
之后的內容,是否有任何可以用來重構它的功能方法?
再添加一個示例:
var queryString = 'select c.id, c.name, t.contact_user '+
'from companies c, teams t '+
'where t.user_id = $1::int and t.company_id = c.id '+
'limit $2::int';
var self = this;
return new Promise(function _promise(resolve, reject) {
req.client.query( queryString, [self.id, User._RESOURCE_LIMIT],
function result(error, result) {
req.done(error);
if (error) {
console.log('Error ' + error.message);
return reject(error);
}
self._companies = result.rows.map(function (data) {
return new Company(data);
});
resolve(self);
});
});
承諾的“查詢”功能
let query = (req, queryString, arg = []) => new Promise((resolve, reject) => {
req.client.query(queryString, arg, (error, result) => {
req.done(error);
if (error) {
return reject(error);
}
resolve(result);
});
});
用法(根據問題中的示例)
query(req, "select * .... etc")
.then(result => {
return result.rows.map(function(row) {
return new User(row);
});
})
.catch(reason => {
// error handling goes here
});
您可以執行以下操作:
function queryDb(queryString, arr) {
var arr = arr || [];
return new Promise(function _promise(resolve, reject) {
req.client.query(queryString, arr, function result(error, result) {
req.done(error);
if (error) {
console.log('Error ' + error.message);
return reject(error);
}
resolve(result);
});
});
}
queryDb("queryString", arr).then(function(response){ //calling the function everytime like this
//do stuff here
}, function(error){
//handle error
})
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