Category: JavaScript Answers

Sometimes, we want to create a simple table with React and JavaScript.

In this article, we’ll look at how to create a simple table with React and JavaScript.

How to create a simple table with React and JavaScript?

To create a simple table with React and JavaScript, we can use the array map method.

For instance, we write:

import React from "react";

const arr = [
  { firstName: "john", lastName: "smith" },
  { firstName: "jane", lastName: "doe" },
  { firstName: "mary", lastName: "smith" }
];

export default function App() {
  const rows = arr.map((a) => {
    const { firstName, lastName } = a;
    return (
      <tr>
        <td>{firstName}</td>
        <td>{lastName}</td>
      </tr>
    );
  });

  return (
    <div>
      <table>
        <tbody>{rows}</tbody>
      </table>
    </div>
  );
}

We call arr.map with a callback that returns the table rows which we create by populating it with the arr entry’s values.

Then we put the row in between the tbody tags to add the rows as the children of tbody.

Therefore, we see:

john	smith
jane	doe
mary	smith

displayed.

Conclusion

To create a simple table with React and JavaScript, we can use the array map method.

Sometimes, we want to match 6 digit hexadecimal numbers with JavaScript regular expressions.

In this article, we’ll look at how to match 6 digit hexadecimal numbers with JavaScript regular expressions.

How to match 6 digit hexadecimal numbers with JavaScript regular expressions?

To match 6 digit hexadecimal numbers with JavaScript regular expressions, we can use the /[0-9A-Fa-f]{6}/g regex.

For instance, we write:

console.log(/[0-9A-Fa-f]{6}/g.test('ffffff'))
console.log(/[0-9A-Fa-f]{6}/g.test('abc'))

to check if 'ffffff' and 'abc' are valid 6 digit hex numbers with the regex test method.

Since 'ffffff' is a valid 6 digit hex number, the first log logs true.

And since 'abc' isn’t a valid 6 digit hex number, the first log logs false.

Conclusion

To match 6 digit hexadecimal numbers with JavaScript regular expressions, we can use the /[0-9A-Fa-f]{6}/g regex.

Sometimes, we want to check if a setInterval timer is running and stop it with JavaScript.

In this article, we’ll look at how to check if a setInterval timer is running and stop it with JavaScript.

How to check if a setInterval timer is running and stop it with JavaScript?

To check if a setInterval timer is running and stop it with JavaScript, we can call clearIntveral with the timer variable.

For instance, we write:

<button>
  stop
</button>

to add a button.

Then we write:

const interval = setInterval(() => {
  console.log('hello')
}, 2000);

const button = document.querySelector('button')
button.onclick = () => {
  clearInterval(interval)
}

to call setInterval with a callback that runs every 2 seconds.

Then we select the button with querySelector.

And we set button.onclick to a function that calls clearInterval to clear the timer.

Conclusion

To check if a setInterval timer is running and stop it with JavaScript, we can call clearIntveral with the timer variable.

Sometimes, we want to use Array.prototype.map with Promise.all in JavaScript.

In this article, we’ll look at how to use Array.prototype.map with Promise.all in JavaScript.

How to use Array.prototype.map with Promise.all in JavaScript?

To use Array.prototype.map with Promise.all in JavaScript, we should call map with a callback that returns a promise.

For instance, we write:

(async () => {
  const items = [1, 2, 3]
  const vals = await Promise.all(items.map(async (it) => it * 2))
  console.log(vals)
})()

to calls items.map with an async function as the callback.

It returns a promise that resolves to the items entry times 2.

Then we call Promise.all with the array of promises we created with map.

Therefore, vals is [2, 4, 6].

Conclusion

To use Array.prototype.map with Promise.all in JavaScript, we should call map with a callback that returns a promise.

Sometimes, we want to clone a div and change the ID’s of it and all it’s children to be unique with JavaScript.

In this article, we’ll look at how to clone a div and change the ID’s of it and all it’s children to be unique with JavaScript.

How to clone a div and change the ID’s of it and all it’s children to be unique with JavaScript?

To clone a div and change the ID’s of it and all it’s children to be unique with JavaScript, we can use the cloneNode method.

For instance, we write:

const div = document.createElement('div')
const div2 = div.cloneNode(true)
div2.id = '2'

We call cloneNode with true to do a deep clone of the div.

Then we assign a new id value to by assigning a value to the id property.

Conclusion

To clone a div and change the ID’s of it and all it’s children to be unique with JavaScript, we can use the cloneNode method.