arrays - 如何遍历数组并根据 PostgreSQL 查询的结果构造对象

Question

这是我的问题:

var ps = ["P1", "P2"];
var hs = ["H1", "H2"];

var jOut = {};

hs.forEach(async (h) => {
    var t = `t_${h}`;
    var query = {
        text: `SELECT pName, pPrice FROM ${t} WHERE pName = ANY($1)`,
        values: [ps],
        rowMode: "array"
    };

    var qres = await client.query(query);
    jOut[t] = qres.rows;
});

console.log(jOut);

我希望输出看起来像这样:

{
    t_H1: [ [pName: "P1", pPrice: 0.5], [pName: "P2", pPrice: 1.2] ],
    t_H2: [ [pName: "P1", pPrice: 0.6], [pName: "P2", pPrice: 1.0] ]
}

但是我的输出看起来像这样:

{}

Answer 1

forEach 循环不会等待 promise 直到它们被解决，这就是为什么

console.log(jOut);

在您的所有/任何 promise 得到解决之前立即执行。

改为使用for..of 循环

for(const h of hs) {
 var t = `t_${h}`;
    var query = {
        text: `SELECT pName, pPrice FROM ${t} WHERE pName = ANY($1)`,
        values: [ps],
        rowMode: "array"
    };

    var qres = await client.query(query);
    jOut[t] = qres.rows;
}
console.log(jOut);