我是异步javascript代码的新手,想在我当前的node.js项目(express.js api)中越来越多地使用它。
我的GET路线有这个功能,它有效,但显然不是正确的方法:
portfolio: function(req, res, next) {
const ethCoins = 0.001;
const ltcCoins = 0.789;
const xrpCoins = 0.987;
const xrbCoins = 0.123;
const btcCoins = 0.321;
let ethSum, btcSum, ltcSum, xrpSum, xrbSum, cryptoSum;
let ethValue = ccHelper.coinInUSD('ETH', ethCoins);
let ltcValue = ccHelper.coinInUSD('LTC', ltcCoins);
let xrpValue = ccHelper.coinInUSD('XRP', xrpCoins);
let xrbValue = ccHelper.coinInUSD('XRB', xrbCoins);
let btcValue = ccHelper.coinInUSD('BTC', btcCoins);
ethValue.then(result => {
ethSum = result;
ltcValue.then(result => {
ltcSum = result;
xrpValue.then(result => {
xrpSum = result;
xrbValue.then(result => {
xrbSum = result;
btcValue.then(result => {
btcSum = result;
let coinSum = ethSum + ltcSum + xrpSum + xrbSum + btcSum;
res.json(coinSum);
})
})
})
})
})
},
ccHelper.coinInUSD函数调用它(需要参考):
coinInUSD: function(crypto, amount){
return cc.price(crypto, 'USD')
.then(prices => {
const priceArray = [];
Object.keys(prices).forEach((key) => {
priceArray.push(prices[key]);
});
let priceSum = priceArray.reduce((a, v) => (a+v), 0);
const currentValue = amount * priceSum;
return currentValue;
}).catch(console.error)
},
有人可以解释我如何避免这种链接以及正确的模式是什么?我这样做是因为我只能设置res.json
一次。
答案 0 :(得分:3)
你可以使用Promise.all来做这件事。
以下是一个例子:
const ethCoins = 0.001;
const ltcCoins = 0.789;
const xrpCoins = 0.987;
const xrbCoins = 0.123;
const btcCoins = 0.321;
let ethValue = ccHelper.coinInUSD('ETH', ethCoins);
let ltcValue = ccHelper.coinInUSD('LTC', ltcCoins);
let xrpValue = ccHelper.coinInUSD('XRP', xrpCoins);
let xrbValue = ccHelper.coinInUSD('XRB', xrbCoins);
let btcValue = ccHelper.coinInUSD('BTC', btcCoins);
Promise.all([ethValue, ltcValue, xrpValue, xrbValue, btcValue]).then(values => {
let coinSum = values.reduce((a, v) => (a+v), 0);
res.json(coinSum);
}).catch(e => console.error(e));