Author: John Au-Yeung

Sometimes, we want to create list of objects in JavaScript.

In this article, we’ll look at how to create list of objects in JavaScript.

How to create list of objects in JavaScript?

To create list of objects in JavaScript, we can put objects in an array.

For instance, we write

const list = [
  { date: "12/1/2022", reading: 3, id: 20055 },
  { date: "13/1/2022", reading: 5, id: 20053 },
  { date: "14/1/2022", reading: 6, id: 45652 },
];

to put 3 objects in the square brackets to populate the list array.

Then we access an object’s value with

console.log(list[1].date);

We use list[1].date to get the 2nd object’s date property value.

Conclusion

To create list of objects in JavaScript, we can put objects in an array.

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.