query in query result loop"/>
[nodejs query in query result loop
我正在使用nodejs / mysql执行mysql查询。
在第一个结果集之后,我将遍历结果集并查询第二个表。
1)为什么“ for”有效而“ foreach”无效?什么是实现我所需的正确循环方式?
2)item = {...项目,图像:行}在getImage函数中也不起作用,为什么?
3)如何让console.log显示修改后的结果?如果我使用“ await”,console.log(rows)应该显示修改后的结果,对吗?
const getImages = async (item, key) => {
let sql = await connection.format('SELECT * from `images` WHERE id = ?', [item.id]);
const [ rows , fields ] = await connection.execute(sql);
item['images'] = rows
item = { ...item, images: rows } //'<-- this method doesn't work.
return item
}
let sql = await connection.format(`SELECT * from table ORDER BY a.listing_id LIMIT ?,?`, [0,10])
var [rows, fields] = await connection.execute(sql);
// rows.forEach(getImages) //'<-- this does not work when uncommented
// rows = rows.forEach(getImages) //'<-- this also does not work when uncommented.
for (let i = 0; i < rows.length; i++) { //'<-- but this works
rows[i] = await getImages(rows[i], i);
}
console.log(rows) //<----- this doesn't show modified results on terminal console
res.json(rows) //<----- browser can see the modified results on browser console
回答如下:您必须将每个项目的正确处理程序传递给foreach方法:
let new_rows = Array()
rows.forEach(row => {
new_rows.push(await getImages(row, i))
});
另外,如果要在另一个数组上获取图像,则应使用更清洁的map:
let new_rows = rows.map(row => {
return await getImages(row, i)
});
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