Category: JavaScript Answers

Sometimes, we want to pass an unknown number of arguments into JavaScript function.

In this article, we’ll look at how to pass an unknown number of arguments into JavaScript function.

How to pass an unknown number of arguments into JavaScript function?

To pass an unknown number of arguments into JavaScript function, we use the rest operator.

For instance, we write

const printNames = (...names) => {
  for (const name of names) {
    console.log(name);
  }
};

to define the printNames function that takes an infinite number of arguments.

We use the ... rest operator to get all the arguments into the names array.

Then we use a for-of loop to loop through all the names entries and print out all the entries into the console.

Conclusion

To pass an unknown number of arguments into JavaScript function, we use the rest operator.

Sometimes, we want to tell setInterval to only fire x amount of times with JavaScript.

In this article, we’ll look at how to tell setInterval to only fire x amount of times with JavaScript.

How to tell setInterval to only fire x amount of times with JavaScript?

To tell setInterval to only fire x amount of times with JavaScript, we call clearInterval after the setInterval callback has been called x times.

For instance, we write

let x = 0;
const intervalID = setInterval(() => {
  // ...
  if (++x === 5) {
    clearInterval(intervalID);
  }
}, 1000);

to call setInterval with a callback that runs every second.

We keep track of the number of times the callback is called with x.

We increment x each time the callback is run.

If x is 5, then we call clearInterval with the intervalID to stop running the setInterval callback after it ran 5 times.

Conclusion

To tell setInterval to only fire x amount of times with JavaScript, we call clearInterval after the setInterval callback has been called x times.

Sometimes, we want to create a text input dynamically with JavaScript.

In this article, we’ll look at how to create a text input dynamically with JavaScript.

How to create a text input dynamically with JavaScript?

To create a text input dynamically with JavaScript, we call the createElement method.

For instance, we write

const input = document.createElement("input");
input.setAttribute("type", "text");

const parent = document.getElementById("parentDiv");
parent.appendChild(input);

to call the document.createElement method to create the input element.

Then we call input.setAttribute to set the type attribute of the input to text.

Next, we select the parent element that the input will be in with getElementById.

Then we call appendChild to append the input as the last child of parent.

Conclusion

To create a text input dynamically with JavaScript, we call the createElement method.

Sometimes, we want to prevent iPhone from zooming in on select in a web app with HTML.

In this article, we’ll look at how to prevent iPhone from zooming in on select in a web app with HTML.

How to prevent iPhone from zooming in on select in a web app with HTML?

To prevent iPhone from zooming in on select in a web app with HTML, we can user-scalable=no in a meta tag.

For instance, we write

<meta
  name="viewport"
  content="width=device-width, minimum-scale=1.0, maximum-scale=1.0, user-scalable=no"
/>

to add user-scalable=no into the content attribute value of the meta element.

This will prevent the iPhone from zooming in when we select text in our web app.

Conclusion

To prevent iPhone from zooming in on select in a web app with HTML, we can user-scalable=no in a meta tag.

Sometimes, we want to check if a key exists in a JavaScript object.

In this article, we’ll look at how to check if a key exists in a JavaScript object.

How to check if a key exists in a JavaScript object?

To check if a key exists in a JavaScript object, we can use the in operator.

For instance, we write

const testArray = "key1" in obj;

to check if property with name 'key1‘ is in the obj object.

Conclusion

To check if a key exists in a JavaScript object, we can use the in operator.