Category: JavaScript Answers

Sometimes, we want to fix JSON.parse unexpected character error with JavaScript.

In this article, we’ll look at how to fix JSON.parse unexpected character error with JavaScript.

How to fix JSON.parse unexpected character error with JavaScript?

To fix JSON.parse unexpected character error with JavaScript, we should make sure that we’re parsing a JSON string with JSON.parse.

For instance, we write

const obj = JSON.parse(JSON.stringify(yourJSONObject));

to call JSON.stringify with yourJSONObject to convert the yourJSONObject object to a JSON string.

Then we call JSON.parse to parse the JSON string to the obj object.

Conclusion

To fix JSON.parse unexpected character error with JavaScript, we should make sure that we’re parsing a JSON string with JSON.parse.

Sometimes, we want to check if an element has event listener on it with JavaScript.

In this article, we’ll look at how to check if an element has event listener on it with JavaScript.

How to check if an element has event listener on it with JavaScript?

To check if an element has event listener on it with JavaScript, we can call the getEventListeners function in the Chrome developer console.

For instance, we write

getEventListeners(document.querySelector("your-element-selector"));

in the Chrome developer console to select the element we want to check with querySelector.

And then we call getEventListeners with the element to get all the event listeners added to the element.

Conclusion

To check if an element has event listener on it with JavaScript, we can call the getEventListeners function in the Chrome developer console.

Sometimes, we want to check if date is less than 1 hour ago with JavaScript.

In this article, we’ll look at how to check if date is less than 1 hour ago with JavaScript.

How to check if date is less than 1 hour ago with JavaScript?

To check if date is less than 1 hour ago with JavaScript, we can compare the timestamp difference to the value for one hour in milliseconds.

For instance, we write

const lessThanOneHourAgo = (date) => {
  const HOUR = 1000 * 60 * 60;
  const anHourAgo = Date.now() - HOUR;

  return date > anHourAgo;
};

to define HOUR to be the value of one hour in milliseconds.

Then we use Date.now() - HOUR to get the timestamp in milliseconds for one hour ago.

Finally, we compare the timestamp of date to anHourAgo with

date > anHourAgo

Conclusion

To check if date is less than 1 hour ago with JavaScript, we can compare the timestamp difference to the value for one hour in milliseconds.

Sometimes, we want to upload multiple files using form data with JavaScript.

In this article, we’ll look at how to upload multiple files using form data with JavaScript.

How to upload multiple files using form data with JavaScript?

To upload multiple files using form data with JavaScript, we can call the append with the same key for multiple files.

For instance, we write

const { files } = document.getElementById("fileupload");
const formData = new FormData();
for (const image of files) {
  formData.append("files", image);
}

to select the file input with getElementById.

Then we get the selected files with files.

Next, we create the FormData object.

Then we loop through the files with a for-of loop and call formData.append with the 'files' key and add each image to it.

Conclusion

To upload multiple files using form data with JavaScript, we can call the append with the same key for multiple files.

Sometimes, we want to fix webpack –watch isn’t compiling changed files with JavaScript.

In this article, we’ll look at how to fix webpack –watch isn’t compiling changed files with JavaScript.

How to fix webpack –watch isn’t compiling changed files with JavaScript?

To fix webpack –watch isn’t compiling changed files with JavaScript, we can increase the number of watchers and ignore files that don’t have to be watched.

We run

echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p

to increase the number of watchers to 524288.

Also, in our Webpack config, we write

//...

module.exports = {
  //...
  watchOptions: {
    poll: true,
    ignored: /node_modules/,
  },
  //...
};

to ignore the /node_modules/ folder in the watch options so that Webpack doesn’t watch anything in the folder for changes.

Conclusion

To fix webpack –watch isn’t compiling changed files with JavaScript, we can increase the number of watchers and ignore files that don’t have to be watched.