Author: John Au-Yeung

To return values from async functions using async-await from function with JavaScript, we return the resolve value of the promise.

For instance, we write

const getData = async () => {
  const { data } = await axios.get(
    "https://jsonplaceholder.typicode.com/posts"
  );
  return data;
};

(async () => {
  console.log(await getData());
})();

to create the getData function that gets the resolve value of the promise returned by axios.get with await.

We extract the data property from the object returned by the promise and return it.

We then use await with getData to get the resolve value of the promise that was returned with return in getData.

Sometimes, we want to import module with a variable name in Node.js.

In this article, we’ll look at how to import module with a variable name in Node.js.

How to import module with a variable name in Node.js?

To import module with a variable name in Node.js, we can call the import function.

For instance, we write

const importModule = async () => {
  try {
    const module = await import("./path/module.js");
  } catch (error) {
    console.error("import failed");
  }
};

to call import with the path string to the module.

It returns a promise with the module that we imported.

So we get the module with await.

Conclusion

To import module with a variable name in Node.js, we can call the import function.

Sometimes, we want to detect when an image fails to load in JavaScript.

In this article, we’ll look at how to detect when an image fails to load in JavaScript.

How to detect when an image fails to load in JavaScript?

To detect when an image fails to load in JavaScript, we can listen for the img element’s error event.

For instance, we write

const imageFound = () => {
  alert("That image is found and loaded");
};

const imageNotFound = () => {
  alert("That image was not found.");
};

const img = new Image();
img.onload = imageFound;
img.onerror = imageNotFound;
img.src = "http://foo.com/bar.jpg";

to create an img element with Image.

Then we set img.onerror to the imageNotFound function.

imageNotFound runs when the img with the img.src URL fails to load.

Conclusion

To detect when an image fails to load in JavaScript, we can listen for the img element’s error event.

Sometimes, we want to skip one test in test file Jest and JavaScript.

In this article, we’ll look at how to skip one test in test file Jest and JavaScript.

How to skip one test in test file Jest and JavaScript?

To skip one test in test file Jest and JavaScript, we can use the skip method.

For instance, we write

test("it is raining", () => {
  expect(inchesOfRain()).toBeGreaterThan(0);
});

test.skip("it is not snowing", () => {
  expect(inchesOfSnow()).toBe(0);
});

to call test.skip to skip the 2nd test.

The first test will be run.

Conclusion

To skip one test in test file Jest and JavaScript, we can use the skip method.

Sometimes, we want to send authorization header with Axios and JavaScript.

In this article, we’ll look at how to send authorization header with Axios and JavaScript.

How to send authorization header with Axios and JavaScript?

To send authorization header with Axios and JavaScript, we can set the headers property in the request options object.

For instance, we write

const response = await axios.get(url, {
  headers: {
    Authorization: `Bearer ${token}`,
  },
});

to make a get request to the url with axios.get.

We set the Authorization header by adding the Authorization property to headers.

And we get the response from the returned promise with await.

Conclusion

To send authorization header with Axios and JavaScript, we can set the headers property in the request options object.