从先前解决的承诺获取属性?

Question

我有一个async函数，在运行fetch和.json()后返回一个对象。我想要有不止一个以对象作为输入的回调。因为我需要链接.then()来调用回调，所以我需要每次都运行抓取函数。

是否有一种方法来获取一次，然后有回调做他们的事情与输出而不必重新获取?

async function getData(){
const response = await fetch('api-url');
return await response.json();
}
function foo(data){
// do stuff
}
function bar(data){
// do stuff
}
const doFoo = getData().then(foo) // I don't want to run getData()
const doBar = getData().then(bar) // each time

我想，我可以将输出保存到缓存，但是有一种方法可以用承诺来做吗?

Answer 1

任何时候，只要你想生成一个值，然后多次使用它:将它存储在一个变量中

const data = getData();
data.then(foo);
data.then(bar);

Answer 2

//to check the state of the promise
undefined === Promise.prototype.state && (Promise.prototype.state = function () {
const t = {};
return Promise.race([this, t]).then(v => (v === t) ? 'pending' : 'fulfilled', () => 'rejected');
});
function promiseWrapper(promiseFunction) {
let getPromise = Promise.reject();
let getFinalData = async function(force) {
let args = [].slice.call(arguments, 1);
//if force available, api will be called
if(force) {
return promiseFunction.apply(this, args);
}

let state = await this.getPromise.state();
//if state is rejected, trigger and fetch the data
'rejected' === state && (this.getPromise = promiseFunction.apply(this, args));
return this.getPromise;
}
//get method first method is force, rest will be treated as arguments
return {getPromise, get: getFinalData};
}

//instead of creating function pass the function in promiseWrapper
//promiseWrapper helps if somehow it is rejected, we wan recall the function without refreshing the page
var getData = promiseWrapper(async function() {
const response = await fetch('https://reqres.in/api/products/3');
return await response.json();
});
function foo(data) {
console.log('foo datan', data)
}
function bar(data) {
console.log('bar datan', data)
}
getData.get().then(foo) //It will trigger the api, because it is first time
getData.get(true).then(bar) //data by calling api
//getData.get(false).then(console.log) and getData.get().then(console.log), will act same