如何等待其他呼叫的响应以创建呼叫后请求

Question

I have below 2 files, I want to make sure the call is in order. I tried the promise and callback, I have to admit, I am not 100% familiar with async calls.

config.js:

import rolesJson from '../../roles';

class Config{

url;
rolesList;

constructor(callback){

    var baseurl = 'www.example.com/env';

    fetch(baseurl)
        .then(response => response.json())
        .then(data => {
            this.url = data.url;
            getAuth(data.env);
    }).catch((error) => {

    });

    const getAuth= (env) => {
        const headers = { 'Content-Type': 'application/json' };
        const options = { method: 'POST', headers, body:JSON.stringify(rolesJson(env))};
        console.log("THIS BODY SHOULD NOT BE UNDEFINED", options.body);
        fetch('www.example.com/auth', options)
            .then(response => response.json())
            .then(data => {

            }).catch((error) => {

            });
    };
}    
}
module.exports = Config;

roles.js

var roleUrl = 'www.example.com/roles';

const setEnviroment = (rolesdata,env) => {
let reqBody = {
    "environment": env,
    "components": rolesdata
}
console.log("REQUEST BODY CREATED", reqBody);
return req;
}

const getRoles = (env) => {
fetch(roleUrl)
.then(response => response.json())
.then(roles => {
    let rolesList = [];
    roles.map(x => {
        const roleObj = {
            name: x.name,
            id: x.id,
        }
        rolesList.push(roleObj);
    })
    return setEnviroment(rolesList, env);
 }).catch((error) => {

});
};
module.exports = getRoles;

How can I make sure when i am calling fetch('www.example.com/auth', options), the options.body is not undefined? I have tried to use async/await and callbacks, nothing works for me.

Any help will be very appreciated.

Thanks

Answer 1

No worries - promises are not easy to get at first. So first of all, you can only rely on the value, if you waited that it was resolved. This can be done, as you already pointed out, with.then or with async / await.

.then-solution:

var roleUrl = 'www.example.com/roles';

const setEnviroment = (rolesdata,env) => {
let reqBody = {
    "environment": env,
    "components": rolesdata
}
console.log("REQUEST BODY CREATED", reqBody);
return req;
}

const getRoles = (env) => {
fetch(roleUrl)
.then(response => response.json())
.then(roles => {
    let rolesList = [];
    roles.map(x => {
        const roleObj = {
            name: x.name,
            id: x.id,
        }
        rolesList.push(roleObj);
    })
    return setEnviroment(rolesList, env);
 });
 // we return the promise
};
module.exports = getRoles;

class Config{

url;
rolesList;

constructor(callback){

    var baseurl = 'www.example.com/env';

    fetch(baseurl)
        .then(response => response.json())
        .then(data => {
            this.url = data.url;
            getAuth(data.env);
    }).catch((error) => {

    });

    const getAuth= (env) => {
        const headers = { 'Content-Type': 'application/json' };
        const options = { method: 'POST', headers, body:JSON.stringify(rolesJson(env))};
        console.log("THIS BODY SHOULD NOT BE UNDEFINED", options.body);
        fetch('www.example.com/auth', options)
            .then(response => response.json());
        // we return the Promise
    };
}    
}
module.exports = Config;

// calling method

Config.getAuth(env).then((value) => {
    return getRoles(env); //this returns a Promise again
}).then(x => {
    // here you have the return type of getRoles
})

async-await-solution:

var roleUrl = 'www.example.com/roles';

const setEnviroment = (rolesdata,env) => {
let reqBody = {
    "environment": env,
    "components": rolesdata
}
console.log("REQUEST BODY CREATED", reqBody);
return req;
}

const getRoles = async (env) => {
    let response await fetch(roleUrl); // awaiting fetch promise
    let roles = await response.json(); // awaiting .json()-promise
    let rolesList = [];
    roles.map(x => {
        const roleObj = {
            name: x.name,
            id: x.id,
        }
        rolesList.push(roleObj);
    })
    return setEnviroment(rolesList, env);
 };
 // async always returns a promise

module.exports = getRoles;

class Config{

url;
rolesList;

constructor(callback){

    var baseurl = 'www.example.com/env';

    fetch(baseurl)
        .then(response => response.json())
        .then(data => {
            this.url = data.url;
            getAuth(data.env);
    }).catch((error) => {

    });

    const getAuth = async (env) => {
        const headers = { 'Content-Type': 'application/json' };
        const options = { method: 'POST', headers, body:JSON.stringify(rolesJson(env))};
        console.log("THIS BODY SHOULD NOT BE UNDEFINED", options.body);
        const response = await fetch('www.example.com/auth', options);
        const body = await response.json();
        return body; // we return a Promise including the body
    };
}    
}
module.exports = Config;

// calling method

const callerMethod = async () => {
    const auth = await Config.getAuth(env);
    const roles = await getRoles(env);
    //now you can work with the resolved stuff
};

Please note, that callerMethod will return a Promise itself again, because it's async.