[英]How to wrap function call inside of Promise
導出所需模塊並設置變量后
let AWS = require("aws-sdk");
const AmazonCognitoIdentity = require('amazon-cognito-identity-js');
const USER_POOL_ID = 'us-east-1_vkXRQuP4U';
const CLIENT_ID = 'mipa4trls0l7323om33mlk80e8';
const poolData = {
UserPoolId : USER_POOL_ID, ClientId : CLIENT_ID
};
const POOL = new AmazonCognitoIdentity.CognitoUserPool(poolData);
let email = "my.email@domain.com";
let password = "My.Password!";
我可以繼續調用signUp
命令:
POOL.signUp(email, password, [], null, function(err, result) {
console.log('...result:', result);
});
它運作良好。 接下來,我想將POOL.signUp(email, password...)
包裝在async
函數sign_up
如下所示:
async function sign_up(email, password) {
POOL.signUp(email, password, [], null, function(err, result) {
console.log('...sign_up.result:', result);
return result;
})
};
async function main() {
let signupData = await sign_up(email, password);
console.log('...main.signupData:', signupData);
return signupData;
};
main().then((error, data) => {console.log('...error, data:', error, data)});
雖然它工作正常,但執行的調用順序是錯誤的,因為main
函數不等待sign_up()
函數完成。 為了糾正這種行為,我將POOL.signUp(email, password...)
包裝在 Promise 中:
async function sign_up(email, password) {
return await new Promise((resolve) => {
POOL.signUp(email, password, [], null, {
onSuccess: (result) => {
console.log('...result:', result)
return resolve(result);
},
onFailure: (err) => {
return resolve(err.message);
},
});
})
};
但我收到錯誤消息:
UnhandledPromiseRejectionWarning: TypeError: callback is not a function
有沒有辦法避免這個錯誤?
await
您返回的 Promise(因為我們確切地希望我們的函數是異步的,我們希望將等待推遲到調用者)Promise
構造函數需要提供第二個reject
參數才能訪問函數實現中的回調POOL.signUp
第四個參數,而不是一個對象function sign_up(email, password) {
return new Promise((resolve, reject) => {
POOL.signUp(email, password, [], null, function(err, result) {
if (err) {
return reject(err.message);
}
console.log('...result:', result)
resolve(result);
});
})
};
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