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[英]http requests inside loop of variable size, how to do something only after last request has finished (JavaScript)
[英]How to get response after Loop of requests finished
我嘗試在每個循環中執行多個請求並將數據響應推送到一個數組,但我總是只得到第一個項目
//Get all roles
router.get('/', async (req, res) =>{
try {
knex.from( roles_table )
.then(roles => {
let rolePermissions =[];
roles.forEach(role => {
knex.select(permissions_table + '.*').from(permissions_table)
.innerJoin(permissions_roles_table, permissions_table + '.id', permissions_roles_table +'.id_permission')
.where(permissions_roles_table + '.id_role', '=', role.id)
.then(rows => {
role.permissions = rows;
rolePermissions.push(role)
});
});
res.status(200).json(rolePermissions);
});
} catch (err) {
res.status(500).json({message: err});
}
});
想做現代JS,必須要了解Promise和asynchrone。
類似的東西可能就是你要找的
//This const will store an array of Promise
const allRows = knex.from( roles_table )
.then(roles => {
return roles.map(role => {
return knex.select(permissions_table + '.*').[...]
});
});
//This method will wait for each promises to succeed or first one to failed
return Promise.all(allRows)
.then( allRows => {
//allRows is now an array containing all the results
res.status(200).json(rolePermissions);
})
.catch (err) {
res.status(500).json({message: err});
});
對了,不需要try/catch一個Promise,有.catch方法
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