Category: JavaScript

Sometimes, we want to merge 2 JavaScript objects, populating the properties in one if they don’t exist in the other.

In this article, we’ll look at how to merge 2 JavaScript objects, populating the properties in one if they don’t exist in the other.

How to merge 2 JavaScript objects, populating the properties in one if they don’t exist in the other?

To merge 2 JavaScript objects, populating the properties in one if they don’t exist in the other, we can use some object methods.

For instance, we write:

const a = {
  'foo': 'bar',
  'baz': 'bat'
};
const b = {
  'foo': 'quux'
};
const entries = Object.entries(a).filter(([key]) => Object.keys(a).includes(key))

const filteredA = Object.fromEntries(entries)
const c = {
  ...b,
  ...filteredA
}
console.log(c)

to make a copy of b and merge the properties that aren’t in b into a and assign the merged object to c.

To do this, we call Object.enttries with a to return a nested array with all the key-value pairs.

Then we call filter on the returned array with a callback that returns an array of key-value pairs that are only in a.

Next, we call Object.fromEntries to converted the nested key-value pair array back to an object.

Finally, we merge b and filteredA into c.

Therefore, c is:

{
  baz: "bat",
  foo: "bar"
}

Conclusion

To merge 2 JavaScript objects, populating the properties in one if they don’t exist in the other, we can use some object methods.

Sometimes, we want to raise 10 to a power in JavaScript.

In this article, we’ll look at how to raise 10 to a power in JavaScript.

How to raise 10 to a power in JavaScript?

To raise 10 to a power in JavaScript, we can use the exponentiation (**) operator.

For instance, we write:

const precision = 5
const result = 10 ** precision;
console.log(result)

to raise 10 the precision power.

Therefore, result is 100000.

Conclusion

To raise 10 to a power in JavaScript, we can use the exponentiation (**) operator.

Sometimes, we want to convert a date in dd/mm/yyyy format to mm/dd/yyyy format in JavaScript.

In this article, we’ll look at how to convert a date in dd/mm/yyyy format to mm/dd/yyyy format in JavaScript.

How to convert a date in dd/mm/yyyy format to mm/dd/yyyy format in JavaScript?

To convert a date in dd/mm/yyyy format to mm/dd/yyyy format in JavaScript, we can split the date string and combine the parts.

For instance, we write:

const date = "24/09/2022";
const [day, month, year] = date.split("/");
const newDate = `${month}/${day}/${year}`
console.log(newDate)

We call date.split with '/' to split the date string by the slashes.

Then we combine the parts that we destructured from the array with ${month}/${day}/${year}.

Therefore, newDate is "09/24/2022".

Conclusion

To convert a date in dd/mm/yyyy format to mm/dd/yyyy format in JavaScript, we can split the date string and combine the parts.

Sometimes, we want to make a loading animation in console application written in JavaScript and Node.js.

In this article, we’ll look at how to make a loading animation in console application written in JavaScript and Node.js.

How to make a loading animation in console application written in JavaScript and Node.js?

To make a loading animation in console application written in JavaScript and Node.js, we can use timers and the process.stdout.write method to write the loading animation characters to the screen.

For instance, we write:

const P = ['\\', '|', '/', '-'];
let x = 0;
const loader = setInterval(() => {
  process.stdout.write(`\r${P[x++]}`);
  x %= P.length;
}, 250);

setTimeout(() => {
  clearInterval(loader);
}, 5000);

We call setInterval with a callback that calls process.stdout.write to write the characters in P with index x to the screen every 250 seconds.

Then we call setTimeout with a callback to clear the loader timer in 5 seconds.

Conclusion

To make a loading animation in console application written in JavaScript and Node.js, we can use timers and the process.stdout.write method to write the loading animation characters to the screen.

Sometimes, we want to set options of a dropdown using JavaScript.

In this article, we’ll look at how to set options of a dropdown using JavaScript.

How to set options of a dropdown using JavaScript?

To set options of a dropdown using JavaScript, we can set the value property of the select element.

For instance, we write:

<select>
  <option value='apple'>Apple</option>
  <option value='orange'>Orange</option>
  <option value='grape'>Grape</option>
</select>

to add a select element.

Then we write:

const select = document.querySelector("select")
select.value = "orange";

to select the select element with querySelector.

And then we set select.value to 'orange' to select the 2nd choice.

We set value to a value that of value attribute in the option element.

Conclusion

To set options of a dropdown using JavaScript, we can set the value property of the select element.