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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
我尝试在每个循环中执行多个请求并将数据响应推送到一个数组,但我总是只得到第一个项目
//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});
}
});
想做现代JS,必须要了解Promise和asynchrone。
类似的东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});
});
对了,不需要try/catch一个Promise,有.catch方法
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