Javascript – Postman SendRequest() – Async requests, promises, awaits and loops

The Postman forums have quite a few topics dedicated to the async nature of sendRequest().

I’m trying to produce a clean example on how this works with reusable code.

I’ve run into some queries around calling the async function within a loop.

The following code show the issue with the async nature of sendRequest().

for (let i = 1; i < 11; i++) {
    let testValue = `request${i}`
    let request = {
        url: 'https://postman-echo.com/get?test=' + testValue,
        method: 'GET',
    }
    pm.sendRequest(request, (err, res) => {
        if (err) {
            console.log(err);
        }
        pm.test(`Request ${i} - status code is 200`, () => {
            pm.expect(res).to.have.status(200);
            let resJson = res.json();
            console.log(resJson.args.test);
        });
    });
};

The requests are unordered, as shown in the console logs.

Using promises and awaits resolves the main issue.

const sendRequest = (req) => {
    return new Promise((resolve, reject) => {
        pm.sendRequest(req, (err, res) => {
            if (err) {
                console.log(err);
                return reject(err);
            }
            resolve(res);
        });
    });
};

(async () => {
    for (let i = 1; i < 11; i++) {
        let testValue = `request${i}`
        let request = {
            url: 'https://postman-echo.com/get?test=' + testValue,
            method: 'GET',
        }
        const response = await sendRequest(request); // wait for promise to be resolved before continuing
        pm.test(`Request ${i} - status code is 200`, () => {
            pm.expect(response).to.have.status(200);
            let resJson = response.json();
            console.log(resJson.args.test);
        });
    }
})();

With the requests now in the correct order.

I wanted to make the async function a bit more re-usable and tried to put the loop outside of the function.

const sendRequest = (req) => {
    return new Promise((resolve, reject) => {
        pm.sendRequest(req, (err, res) => {
            if (err) {
                console.log(err);
                return reject(err);
            }
            resolve(res);
        });
    });
};

async function asyncCall(request) {
    const response = await sendRequest(request);
    pm.test(`Request ${i} - status code is 200`, () => {
        pm.expect(response).to.have.status(200);
        let resJson = response.json();
        console.log(resJson.args.test);
    });
};


for (let i = 1; i < 11; i++) {
    let request = {
        url: 'https://postman-echo.com/get?test=' + `request${i}`,
        method: 'GET',
    }
    asyncCall(request);
};

This sends the requests, but they are no longer in order.

The tests aren’t running either.

What am I doing wrong with this approach.