Category: JavaScript Answers

Sometimes, we want to clear an input value after form submission in a React app.

In this article, we’ll look at how to clear an input value after form submission in a React app.

Clear an Input Value After Form Submission in a React App

To clear an input value after form submission in a React app, we can set the value of the input value states after the form is submitted.

For instance, we can write:

import { useState } from "react";

export default function App() {
  const [city, setCity] = useState("");

  const onHandleSubmit = (e) => {
    e.preventDefault();
    setCity("");
  };

  return (
    <div className="App">
      <form onSubmit={onHandleSubmit}>
        <input
          onChange={(e) => setCity(e.target.value)}
          value={city}
          type="text"
        />
        <button type="submit">Search</button>
      </form>
    </div>
  );
}

We create the city state with the useState hook.

Then we create the onHandleSubmit function that’s run when we submit the form with the Search button.

In the function, we call e.preventDefault() to prevent the default server-side form submission behavior.

Then we call setCity with an empty string to empty the city value, which is used as the value of the input.

In the input, we set the onChange prop to a function that calls setCity to set the city value to e.target.value , which has the inputted value.

And in the form element, we set onSubmit to onHandleSubmit to run the it when we submit the form.

Conclusion

To clear an input value after form submission in a React app, we can set the value of the input value states after the form is submitted.

Sometimes, we want to convert a boolean to an integer with JavaScript.

In this article, we’ll look at how to convert a boolean to an integer with JavaScript.

Convert a Boolean to an Integer with JavaScript

To convert a boolean to an integer with JavaScript, we can use the Number function.

For instance, we write:

console.log(Number(true))  
console.log(Number(false))

then we get 1 and 0 in the console log respectively.

We just pass true and false as arguments into the Number function to do the conversion.

Conclusion

To convert a boolean to an integer with JavaScript, we can use the Number function.

Sometimes, we want to invert color on all elements of a page with JavaScript.

In this article, we’ll look at how to invert color on all elements of a page with JavaScript.

Invert Color on All Elements of a Page with JavaScript

To invert color on all elements of a page with JavaScript, we just set use the invert(100%) value with CSS.

For instance, if we have:

<div style='background-color: white'>
  hello
</div>

Then we can invert all the colors by writing:

const css = `html {
  -webkit-filter: invert(100%);
  -moz-filter: invert(100%);
  -o-filter: invert(100%);
  -ms-filter: invert(100%);
}`
const head = document.head
const style = document.createElement('style')
style.type = 'text/css';
if (style.styleSheet) {
  style.styleSheet.cssText = css;
} else {
  style.appendChild(document.createTextNode(css));
}
head.appendChild(style);

We create the css string to set the filter property to invert(100%) on the html element.

Then we get the head element with document.head .

Then we create the style element with document.createElement .

We set the type attribute of style by assigning a value to style.type .

And then we apply the styles from the css string with:

if (style.styleSheet) {
  style.styleSheet.cssText = css;
} else {
  style.appendChild(document.createTextNode(css));
}
head.appendChild(style);

to set the content of the style element and append it to the head with head.appendChild .

Conclusion

To invert color on all elements of a page with JavaScript, we just set use the invert(100%) value with CSS.

Sometimes, we want to retrieve the name from an email address with JavaScript.

In this article, we’ll look at how to retrieve the name from an email address with JavaScript.

Retrieve the Name from an Email Address with JavaScript

To retrieve the name from an email address with JavaScript, we can use the JavaScript string’s lastIndexOf and substring methods to get the part before the last @ from the email address string.

For instance, we write:

const email = "john.doe@example.com";  
const name = email.substring(0, email.lastIndexOf("@"));  
console.log(name)

We get the index of the last @ in the email string with:

email.lastIndexOf("@")

And we call email.substring with 0 and the index returned by lastIndexOf to get the name part of the email string and assign it to name .

Therefore, name is 'john.doe’ according to the console log.

Conclusion

To retrieve the name from an email address with JavaScript, we can use the JavaScript string’s lastIndexOf and substring methods to get the part before the last @ from the email address string.

Sometimes, we want to apply the ESLint no-unused-vars rule to a block of JavaScript code.

In this article, we’ll look at how to apply the ESLint no-unused-vars rule to a block of JavaScript code.

Apply the ESLint no-unused-vars Rule to a Block of JavaScript Code

To apply the ESLint no-unused-vars rule to a block of JavaScript code, we can wrap the code block that we want to apply the rule to with /* eslint-disable no-unused-vars */ and /* eslint-enable no-unused-vars */ respectively.

For instance, we write:

/* eslint-disable no-unused-vars */

let x;
//...

/* eslint-enable no-unused-vars */

to wrap the code that we want the rule to apply with the comments.

Therefore, the no-unused-vars rule will only apply to the block that are wrapped by the comments.

Conclusion

To apply the ESLint no-unused-vars rule to a block of JavaScript code, we can wrap the code block that we want to apply the rule to with /* eslint-disable no-unused-vars */ and /* eslint-enable no-unused-vars */ respectively.