I'm trying to send a GET request, parse its response and return it to another method. Apparently I have problems handling the asynchronous response.
I want to use Node.js' standard modules, so no Axios.
// class 1: Calling API, processing and returning the response
export async function getData() {
let str = '';
const options = {
hostname: 'jsonplaceholder.typicode.com',
path: '/posts/',
method: 'GET',
json: true,
};
https
.get(options, response => {
response.on('data', chunk => {
str += chunk;
});
response.on('end', () => {
return parseJson(str);
});
})
.on('error', error => {
console.log(error);
});
}
async function parseJson(str) {
const json = JSON.parse(str);
var text;
try {
json.forEach(element => {
text += element.body;
});
// console.log(text); // I'm getting the expected output
return text;
} catch (error) {
console.log('error');
}
}
// class 2: Calling the 2 methods above
getData().then(function (value) {
console.log('DATA: ' + value); // this is called first
});
Unfortunately as output I get an undefined. Despite using async and then:
DATA: undefined
Change getData as follows
export function getData() {
return new Promise((resolve, reject) => {
let str = '';
const options = {
hostname: 'jsonplaceholder.typicode.com',
path: '/posts/',
method: 'GET',
json: true,
};
https.get(options, response => {
response.on('data', chunk => {
str += chunk;
});
response.on('end', () => {
try {
const result = parseJson(str);
resolve(result);
} catch (error) {
reject(error);
}
});
response.on('error', reject);
})
.on('error', reject);
});
}
Now it returns a Promise, which resolves to the result of parseJson(str) or rejects with the error at on('error'
And parseJson as follows - doesn't need to be async since there's nothing asynchronous about the code inside it
Also, removing the try/catch in parseJson and using try/catch in .on("end" means that you can reject the promise returned by getData if there's an error in the parseJson call
function parseJson(str) {
const json = JSON.parse(str);
let text = '';
json.forEach(element => {
text += element.body;
});
return text;
}
alternatively (IMHO better)
function parseJson(str) {
const data = JSON.parse(str); // call it data, not json
return data.map(({body}) => body).join('');
}
or even
const parseJson = (str) => JSON.parse(str).map(({body}) => body).join('');
But that's not important :p
You didn't return anything in the getData. Try this
export async function getData() {
let str = '';
const options = {
hostname: 'jsonplaceholder.typicode.com',
path: '/posts/',
method: 'GET',
json: true,
};
return https
.get(options, response => {
response.on('data', chunk => {
str += chunk;
});
response.on('end', () => {
return parseJson(str);
});
})
.on('error', error => {
console.log(error);
});
}