Author: John Au-Yeung

Web developer specializing in React, Vue, and front end development.

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React Answers

How to Fix the ‘Unknown Prop Warning’ When Developing React Apps?

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Sometimes, we may run into the ‘Unknown Prop Warning’ when developing React apps.

In this article, we’ll look at how to fix the ‘Unknown Prop Warning’ when developing React apps.

Fix the ‘Unknown Prop Warning’ When Developing React Apps

To fix the ‘Unknown Prop Warning’ when developing React apps, we should make sure that we’re passing in props to an element that are recognized as valid attributes.

For instance, if we have:

const Foo = (props) => {
  if (props.layout === 'horizontal') {
    return <div {...props} style={getHorizontalStyle()} />
  } else {
    return <div {...props} style={getVerticalStyle()} />
  }
}

Then we all the properties of props as props of the div element.

This means that the layout prop is also passed in as a prop of the div.

However, layout is not a valid attribute of the div, so we’ll get the ‘unknown prop’ warning in the console as a result.

To make sure we’re only passing in valid properties to the divs, we should destructure the props, we want to pass in.

For instance, we can write:

const Foo = ({ layout, ...rest }) => {
  if (layout === "horizontal") {
    return <div {...rest} style={getHorizontalStyle()} />;
  } else {
    return <div {...rest} style={getVerticalStyle()} />;
  }
};

to use the rest syntax to of the rest object that excludes the layout property.

Then we can spread the rest object properties as props of the div.

Assuming rest property names are all valid attribute names, we shouldn’t get the warning anymore.

Conclusion

To fix the ‘Unknown Prop Warning’ when developing React apps, we should make sure that we’re passing in props to an element that are recognized as valid attributes.

Categories
JavaScript Answers

How to Load Scripts After the Page has Loaded in JavaScript?

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Sometimes, we want to load scripts after the page has loaded in JavaScript.

In this article, we’ll look at how to load scripts after the page has loaded in JavaScript.

Load Scripts After the Page has Loaded in JavaScript

To load scripts after the page has loaded in JavaScript, we can call the jQuery getScript method after the document has been loaded.

We can also listen to the DOMContentLoaded event with plain JavaScript.

For instance, we can write:

$(document).ready(() => {  
  $.getScript("https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js", () => {  
    console.log("Script loaded and executed.");  
  });  
})

We call getScript in the $(document).ready callback so that it’s run only when the DOM is loaded.

To do the same thing with plain JavaScript, we can listen to the DOMContentLoaded event.

To do this, we write:

document.addEventListener('DOMContentLoaded', () => {  
  const script = document.createElement('script');  
  script.src = 'https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js';  
  document.body.appendChild(script);  
});

We call document.addEventListener to add the event listener.

Then in the event listener, we call document.createElement to create the script element.

And we set the src attribute by setting the src property.

Finally, we call document.body.appendChild to append it to the body.

Conclusion

To load scripts after the page has loaded in JavaScript, we can call the jQuery getScript method after the document has been loaded.

Categories
JavaScript Answers

How to Accept an Unlimited Number of Arguments in a JavaScript Function?

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Sometimes, we want to accept an unlimited number of arguments in a JavaScript function.

In this article, we’ll look at how to accept an unlimited number of arguments in a JavaScript function.

Accept an Unlimited Number of Arguments in a JavaScript Function

To accept an unlimited number of arguments in a JavaScript function, we can use the rest operator in the function signature.

For instance, we write:

const foo = (a, b, ...others) => {
  console.log(a, b);
  for (const val of others) {
    console.log(val);
  }
}

foo(1, 2, 3, 4, 5);

We have the foo function that has the parameters a , b , and others .

others has the 3 dots before it, which is the rest operator.

The 3rd and subsequent arguments that are passed into foo will be put into the others array.

Therefore, a is 1, b is 2, and the for-of loop will log 3, 4, and 5.

Conclusion

To accept an unlimited number of arguments in a JavaScript function, we can use the rest operator in the function signature.

Categories
JavaScript Answers

How to Check if an Object is not an Array in JavaScript?

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Sometimes, we want to check if an object is not an array in JavaScript

In this article, we’ll look at how to check if an object is not an array in JavaScript.

Check if an Object is not an Array in JavaScript

To check if an object is not an array in JavaScript, we can use the Array.isArray method.

For instance, we write:

const arr = [1, 2, 3];
console.log(!Array.isArray(arr));

const obj = {}
console.log(!Array.isArray(obj));

We call Array.isArray with arr as its argument to see if arr is an array.

Then we negate the returned value to check if it’s not an array.

Since arr is an array, the console log should log false .

Then we call Array.isArray with obj as its argument to see if obj is an array.

Then we negate the returned value to check if it’s not an array.

Since obj is not an array, the console log should log true.

Conclusion

To check if an object is not an array in JavaScript, we can use the Array.isArray method.

Categories
JavaScript Answers

How to Detect if a JavaScript String Contains Any Spaces?

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Sometimes, we want to detect if a JavaScript string contains any spaces.

In this article, we’ll look at how to detect if a JavaScript string contains any spaces.

Detect if a JavaScript String Contains Any Spaces

To detect if a JavaScript string contains any spaces, we can use the JavaScript regex test method.

For instance, we can write:

const str = 'foo bar'
console.log(/\s/.test(str))

We call .test on the /\s/ regex to check if str has any spaces.

Since str has a space, the console log should log true .

Conclusion

To detect if a JavaScript string contains any spaces, we can use the JavaScript regex test method.