Question

let func1 = function() {
   return new Promise((resolve,reject) => {
        let someVal = 5;
        if (condition) {
            resolve(someVal);
        }
        else {
            reject('error occured');
        }
   });
}

let callingFunction = function() {
    func1().then((res) => {
        console.log("result",res); /* want to return res to the callingFunction */
        return res; /* doesn't work as it returns to the .then not to the callingFunction I guess. */
    });
}

let finalData = callingFunction();

将.then承诺块的结果发送到callingFunction是否可行，以便在finalData中得到结果？

Answer 1

let callingFunction = function() {
  return func1().then((res) => {
    console.log("result",res)
    return res
  })
}
callingFunction().then((res) => {
  let finalData = res
})

Answer 2

问题是promise是一个异步操作，因此let finalData = callingFunction();计算为 undefined 。如果您想在callingFunction()中使用promise的结果，只需将res作为参数传递给它：

let func1 = function() {
   return new Promise((resolve,reject) => {
        let someVal = 5;
        if (condition) {
            resolve(someVal);
        }
        else {
            reject('error occured');
        }
   });
}

func1().then((res) => {
    console.log("result",res); /* want to return res to the callingFunction */
    callingFunction(res);
  });

将promise数据返回给调用函数

2 个答案: