Author: John Au-Yeung

Sometimes, we want to get Firebase Auth User UID with JavaScript.

In this article, we’ll look at how to get Firebase Auth User UID with JavaScript.

How to get Firebase Auth User UID with JavaScript?

To get Firebase Auth User UID with JavaScript, we call onAuthStateChanged.

For instance, we write

firebase.auth().onAuthStateChanged((user) => {
  if (user) {
    // ...
    console.log(user.uid);
  } else {
    // ...
  }
});

to call onAuthStateChanged with a callback that gets the user.

And we get the user.uid if user is set, which means the user is logged in.

Conclusion

To get Firebase Auth User UID with JavaScript, we call onAuthStateChanged.

Sometimes, we want to call addEventListener on a querySelectorAll() with classList with JavaScript.

In this article, we’ll look at how to call addEventListener on a querySelectorAll() with classList with JavaScript.

How to call addEventListener on a querySelectorAll() with classList with JavaScript?

To call addEventListener on a querySelectorAll() with classList with JavaScript, we use forEach to loop through each element.

For instance, we write

const cbox = document.querySelectorAll(".box");
cbox.forEach((box) => {
  box.addEventListener("click", () => box.classList.toggle("red"));
});

to select all elements with class box with querySelectorAll.

Then we call forEach to loop through the node list with a callback.

In it, we call addEventListener to add a click event listener to each element.

And we use a function that calls classList.toggle to toggle the red class as the click listener.

Conclusion

To call addEventListener on a querySelectorAll() with classList with JavaScript, we use forEach to loop through each element.

To clear text area on click with JavaScript, we set the text area’s value property to an empty string.

For instance, we write

<textarea id="text-area" value="Your text inside the textarea"> </textarea>
<button onClick="clear();">Your button Name</button>

to add a text area and a button.

We set onclick to clear(); to call the clear function when we click it.

Then we write

function clear() {
  document.getElementById("text-area").value = "";
}

to define the clear function that selects the text area with getElementById.

And we clear its value by setting its value property to an empty string.

Conclusion

To clear text area on click with JavaScript, we set the text area’s value property to an empty string.

Sometimes, we want to convert binary representation of number from string to integer number in JavaScript.

In this article, we’ll look at how to convert binary representation of number from string to integer number in JavaScript.

How to convert binary representation of number from string to integer number in JavaScript?

To convert binary representation of number from string to integer number in JavaScript, we use the parseInt function.

For instance, we write

const a = parseInt("01001011", 2);

to call parseInt with a binary string and 2 to return the decimal value of the binary string.

The 2nd argument is the radix.

Conclusion

To convert binary representation of number from string to integer number in JavaScript, we use the parseInt function.