React is a popular library for creating web apps and mobile apps.
In this article, we’ll look at some tips for writing better React apps.
Conditionally Pass Prop Inline to a Component
We can conditionally pass prop inline to a component by passing in an expression as the prop value.
For instance, we can write:
<Child {...(this.props.canEdit ? { editOptions : this.state.options } : undefined)} >
We check the canEdit
prop to see if it’s truthy.
If it is, then we pass in the editOptions
prop to the child.
Otherwise, we passed in undefined
.
We use the spread operator to spread the returned objects into props.
Use One or Many useEffect Hooks in a React Component
We can use the useEffect
hook as many times as we want.
For instance, we can write:
useEffect(() => {
// run code
return () => {
// run clean up code
}
}, []);
useEffect(() => {
// run code when props.foo changes
return () => {
// run clean up code when props.foo changes
}
}, [props.foo])
The first useEffect
call is used for running code when the component loads.
The function we return is run when the component unmounts.
In the 2nd useEffect
call, we run code when props.foo
changes.
And the function that’s return runs clean up code when props.foo
changes.
It’s useful for triggering any side effects like an API call or anything like that.
Pass Properties Object to Child Component
We can pass an object’s properties to a child component by using the object spread operator.
For instance, we can write:
return <Child {...props} />;
The all the properties in the props
object will be passed into Child
as props.
Avoid Binding ‘this’ to Every Method
We can avoid binding all our methods to this
by using class fields.
This isn’t part of the JavaScript syntax, but it can be used with Babel or TypeScript.
For instance, we can wire:
class Foo extends React.Component {
onClick = () => {
console.log('clicked');
};
onMouseOver = () => {
console.log('mouse over');
};
render() {
return (
<div
onClick={this.onClick}
onMouseOver={this.onMouseOver}
/>
);
}
}
It’s still in Stage 3, so it’s not final.
Push Method in React Hooks
We can’t use the push
method to append an item to an array since it returns the item that’s appended and changes the array in place.
Instead, we’ve to return a new array with the item that we wan tot append.
For instance, we can write:
const [array, setArray] = useState(initialArray);
Then we write:
setArray(oldArray => [...oldArray, newItem]);
We get the old array and return a new array with the items appended.
The existing items are spread into the new array with the spread operator.
PropTypes Check Object with Dynamic Keys
We can use a function to check an object with dynamic keys when we validate props.
For instance, we can write:
someProp: (props, propName, componentName) => {
if (!/match/.test(props[propName])) {
return new Error('match prop doesn't exist');
}
}
We check if the value of someProp
if the value of someProp
matches the regex pattern we specified.
If it doesn’t then we throw an error.
props
has the props as an object.
propName
has the name of the prop.
componentName
has the component name.
React propTypes: objectOf vs shape
The objectOf
method methods lets us check if a prop value is of a certain type.
For instance, we can write:
number: PropTypes.objectOf(PropTypes.number)
to check if the value of the number
prop is an object.
On the other hand, shape
lets us check for the structure of an object.
For instance, we can write:
styleObj: PropTypes.shape({
color: PropTypes.string,
fontSize: PropTypes.number
}),
Then the styleObj
prop has to have the color
property, which is a string.
And it should have a fontSize
property which is a number.
Conclusion
There are various ways to check the shape of an object we pass in as props.
We can pass properties into an object optionally by specifying a ternary expression.
Also, we can use useEffect
multiple times in our component.
Dynamic keys can also be checked with custom functions with the prop-types package.