I'm new to React and I've made a navbar that displays the users name user
<NavItem eventKey={4} href="#">{this.state.name}</NavItem>
but the problem is if the user is not signed in, I get an error due to this.state.name being undefined. Is there some way I can check if this.state.name is defined before rendering it as part of the navbar or is there a better way to get rid of this error?
To check if an element exists in an array in React: Use the includes() method to check if a primitive exists in an array. Use the some() method to check if an object exists in an array.
Use the useEffect hook to listen for state changes in React. You can add the state variables you want to track to the hook's dependencies array and the logic in your useEffect hook will run every time the state variables change.
Sure, use a ternary:
render() {
return (
this.state.name ? <NavItem>{this.state.name}</NavItem> : null
);
}
or even shorter
render() {
return (
this.state.name && <NavItem>{this.state.name}</NavItem>
);
}
Sure you can:
let userNavItem
if (this.state.name !== undefined) {
userNavItem = <NavItem eventKey={4} href="#">{this.state.name}</NavItem>
} else {
userNavItem = null
}
Now you can use userNavItem
on your navbar component, and it will render only if this.state.name
is defined.
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