如何使用 javascript 访问从 function 返回的 object 的属性？

Question

我有一个返回 object 的方法。 我如何检索该 object 的属性

下面是我的代码，

const called_method = async (context, user) => {
    const available = await context.dbHandler({
        sql:
           'SELECT SUM(first) AS first, SUM(second) AS second FROM items;',
           values: { id: user[0].comp_id },
    });
    return available[0];
};


const some_method = () => {
    const available = called_method(context, user);
    const data = {
        first: available.first, //here i get error says first doesnt exist on type promise
        second: available.second, //here i get error says first doesnt exist on type promise
   }
}

我如何从被调用的方法中返回第一个和第二个并在 some_method 中访问它。

soemone 可以帮我解决这个问题。 谢谢。

Answer 1

异步函数总是返回 promise，因此如果你想获得它的值，你必须等到它稳定下来。 您也可以将some_method设置为异步 function ：

const some_method = async () => {
    const available = await called_method(context, user); // wait until the promise settles
    const data = {
        first: available.first, 
        second: available.second
   }
}

Answer 2

要与 promise 的最终值交互，您需要使用它的.then方法：

const some_method = () => {
  called_method(context, user)
    .then(available => {
      const data = {
        first: available.first,
        second: available.second,
      }
    });
}

或者您需要将代码放入async function 并await promise

const some_method = async () => {
  const available = await called_method(context, user);
  const data = {
     first: available.first,
     second: available.second,
  }
}

Answer 3

您必须等待异步 function：

const called_method = async (context, user) => {
const available = await context.dbHandler({
    sql:
       'SELECT SUM(first) AS first, SUM(second) AS second FROM items;',
       values: { id: user[0].comp_id },
});
return available[0];
};


const some_method = () => {
    called_method(context, user).then(function(available) {
      const data = {
        first: available.first, //here i get error says first doesnt exist on type promise
        second: available.second, //here i get error says first doesnt exist on type promise
      }
  }
}

或者你也可以让你的一些方法异步并等待被调用的方法：

const called_method = async (context, user) => {
const available = await context.dbHandler({
    sql:
       'SELECT SUM(first) AS first, SUM(second) AS second FROM items;',
       values: { id: user[0].comp_id },
});
return available[0];
};


const some_method = async () => {
    const available = await called_method(context, user);
    const data = {
        first: available.first, //here i get error says first doesnt exist on type promise
        second: available.second, //here i get error says first doesnt exist on type promise
    }
}