Can you set a single key of a default prop value object when instantiating a component while leaving the others alone? - Reactjs

CodyLee
March 11, 2023
112 views
0 votes
2 Answers

I’ve created a component that has default values of its props to be objects. Am I able to pass in a value for only 1 of the keys while leaving the others as default?

Example:

Let’s say this is the component:

export default function PageHeader({
  heading = {
    options: "",
    customStyles: {},
    text: ""
  }
}) {
  return (
      <h1 className={heading.options} style={heading.customStyles}>
        {heading.text}
      </h1>
  );
}

Assuming the only thing I want to change from the default prop object’s values is the text. Is there a way for me to do something like this:

<PageHeader heading = {...heading, text: 'New Text'} />

<PageHeader heading.text='New Text' />

Or would I have to pass in the entire heading prop object/not use an object and have each key be its own standalone prop?

Tags: reactjs

Answers

- EnakNalla
- March 11, 2023 at 10:37 pm
- 0 votes
0
If you are set on passing the object you can do it a few ways.

Consider this
```
const defaultHeading = {
  options: {},
  customStyles: {},
  text: ""
}

export function Heading(props) {
  const heading = {...defaultHeading, ...props.heading} // combine so null values are overridden

return (
      <h1 className={heading.options} style={heading.customStyles}>
        {heading.text}
      </h1>
  );
}
```
Or you can use null-coalescing
```
export function Heading({ heading }) {
  
return (
      <h1 className={heading.options ?? {}} style={heading.customStyles ?? {}}>
        {heading.text ?? ""}
      </h1>
  );
}
```
and call like so, only specifying the properties you want to change from default

<PageHeader heading={{ text: "some other text" }} />
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- MattCarlotta
- March 11, 2023 at 10:59 pm
- 0 votes
0
I’d recommend using flattened properties instead of a header object with properties. You can leverage defaultProps to achieve the result you want without manually merging props:
```
import type { CSSProperties, ReactNode } from "react";

export default function PageHeader({
  className,
  style,
  children
}: {
  className?: string;
  style?: CSSProperties;
  children?: ReactNode;
}) {
  return (
    <h1 className={className} style={style}>
      {children}
    </h1>
  );
}

PageHeader.defaultProps = {
  className: "default-class",
  style: { textTransform: "uppercase" },
  children: "Default"
};
```
Here’s a demo utilizing the above code:
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