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Conditional rendering in React based on current component state

I am struggling with figuring out how to implement conditional rendering in React. Basically, what I want to do is this: if there is a reviewResponse in the reviewResponses array, I no longer want to render the reviewResponseForm. I only want to render that ReviewResponse. In other words, each review can only have one response in this app.
I am not sure what I am doing wrong when trying to implement this logic. I know I need to implement some kind of conditional statement saying if the length of my reviewResponses array is greater than 0, I need to render the form. Otherwise, I need to render that reviwResponse. Every statement I have written has not worked here. Does anybody have a suggestion?
Here is my code so far:
My review cardDetails component renders my ReviewResponseBox component and passed the specific reviewId as props:
import React from "react";
import { useLocation } from "react-router-dom";
import StarRatings from "react-star-ratings";
import ReviewResponseBox from "../ReviewResponse/ReviewResponseBox";
const ReviewCardDetails = () => {
const location = useLocation();
const { review } = location?.state; // ? - optional chaining
console.log("history location details: ", location);
return (
<div key={review.id} className="card-deck">
<div className="card">
<div>
<h4 className="card-title">{review.place}</h4>
<StarRatings
rating={review.rating}
starRatedColor="gold"
starDimension="20px"
/>
<div className="card-body">{review.content}</div>
<div className="card-footer">
{review.author} - {review.published_at}
</div>
</div>
</div>
<br></br>
{/*add in conditional logic to render form if there is not a response and response if there is one*/}
<ReviewResponseBox review_id={review.id}/>
</div>
);
};
export default ReviewCardDetails;
Then eventually I want this component, ReviewResponseBox, to determine whether to render the responseform or the reviewresponse itself, if it exists already.
import React from 'react';
import ReviewResponse from './ReviewResponse';
import ReviewResponseForm from './ReviewResponseForm';
class ReviewResponseBox extends React.Component {
constructor() {
super()
this.state = {
reviewResponses: []
};
}
render () {
const reviewResponses = this.getResponses();
const reviewResponseNodes = <div className="reviewResponse-list">{reviewResponses}</div>;
return(
<div className="reviewResponse-box">
<ReviewResponseForm addResponse={this.addResponse.bind(this)}/>
<h3>Response</h3>
{reviewResponseNodes}
</div>
);
}
addResponse(review_id, author, body) {
const reviewResponse = {
review_id,
author,
body
};
this.setState({ reviewResponses: this.state.reviewResponses.concat([reviewResponse]) }); // *new array references help React stay fast, so concat works better than push here.
}
getResponses() {
return this.state.reviewResponses.map((reviewResponse) => {
return (
<ReviewResponse
author={reviewResponse.author}
body={reviewResponse.body}
review_id={this.state.review_id} />
);
});
}
}
export default ReviewResponseBox;
Here are the ReviewResponseForm and ReviewResponse components:
import React from "react";
class ReviewResponseForm extends React.Component {
render() {
return (
<form className="response-form" onSubmit={this.handleSubmit.bind(this)}>
<div className="response-form-fields">
<input placeholder="Name" required ref={(input) => this.author = input}></input><br />
<textarea placeholder="Response" rows="4" required ref={(textarea) => this.body = textarea}></textarea>
</div>
<div className="response-form-actions">
<button type="submit">Post Response</button>
</div>
</form>
);
}
handleSubmit(event) {
event.preventDefault(); // prevents page from reloading on submit
let review_id = this.review_id
let author = this.author;
let body = this.body;
this.props.addResponse(review_id, author.value, body.value);
}
}
export default ReviewResponseForm;
import React from 'react';
class ReviewResponse extends React.Component {
render () {
return(
<div className="response">
<p className="response-header">{this.props.author}</p>
<p className="response-body">- {this.props.body}</p>
<div className="response-footer">
</div>
</div>
);
}
}
export default ReviewResponse;
Any advice would be helpful, thank you.

If I understand your question correctly, you want to render ReviewResponseForm if the this.state.reviewResponses state array is empty.
Use the truthy (non-zero)/falsey (zero) array length property to conditionally render either UI element.
render () {
const reviewResponses = this.getResponses();
const reviewResponseNodes = <div className="reviewResponse-list">{reviewResponses}</div>;
return(
<div className="reviewResponse-box">
{reviewResponses.length
? (
<>
<h3>Response</h3>
{reviewResponseNodes}
</>
)
: (
<ReviewResponseForm addResponse={this.addResponse.bind(this)}/>
)}
</div>
);
}

Creating a popup in ReactJs

I am new in ReactJs and trying to create a popup window through onclick event.
I am following this resource - https://dev.to/skptricks/create-simple-popup-example-in-react-application-5g7f
File - /src/components/feed.js
import React from 'react';
function feed (props) {
return (
<div className="card-header">
<h2>{props.firstname} {props.middleInitial} {props.lastname}</h2>
<h4 className="card-title">{props.gender}</h4>
</div>
<div className="card-footer">
<button onClick="" className="btn btn-secondary">Click To view Samples</button>
</div>
);
}
export default feed;
File - /src/app.js
import React, { Component } from 'react';
import './App.css';
import Header from './components/header.js';
import fetchfeed from './components/fetchfeed.js';
class App extends Component {
render() {
return (
<div>
<Header />
<div className="d-flex justify-content-center">
<fetchfeed />
</div>
</div>
);
}
}
export default App;
File - /src/components/fetchfeed.js
import React from 'react';
import axios from 'axios';
import Pagination from "react-js-pagination";
import feed from './feed.js';
class fetchfeed extends React.Component {
constructor(props) {
super(props);
this.state = {
feedDetails: []
};
this.fetchURL = this.fetchURL.bind(this);
}
fetchURL() {
axios.get(`/feed/`)
.then( response => {
..............
});
//Fetch the feed url and process the variables and setstate to feedDetails array.
}
componentDidMount () {
this.fetchURL()
}
populateRowsWithData = () => {
const feedData = this.state.feedDetails.map(feed => {
return <feed
key = {feed.id}
firstname = {feed.firstname}
middleInitial = {feed.middleInitial}
lastname = {feed.lastname}
dateOfBirth = {feed.dateString}
gender = {feed.gender}
/>;
});
return feedData
}
render(){
return (
<div >
{this.populateRowsWithData()}
</div>
);
}
}
export default fetchfeed;
I have already created Popup.js under /src/components and the required css for the popup as directed on reference link.
My question is where should I define the onclick function for popup?
Any help is highly appreciated. Thanks in advance.

As it says in the source you should do something like this in the component you want to show the popup in:
//This is the function
togglePopup() {
this.setState({
showPopup: !this.state.showPopup
});
}
// This is what you should do in the render method
{this.state.showPopup ?
<Popup
text='Click "Close Button" to hide popup'
closePopup={this.togglePopup.bind(this)}
/>
: null
}

As per my understanding, you are trying to customize the code in the tutorial according to your requirements. If you want to open the popup on click of the button "click to view samples", you should do two things first.
Define a function to trigger when button is clicked
Attach that function to the button
The following code demonstrates above steps.
import React from 'react';
function feed (props) {
function openPopup(){
//code relevant to open popup
}
return (
<div className="card-header">
<h2>{props.firstname} {props.middleInitial} {props.lastname}</h2>
<h4 className="card-title">{props.gender}</h4>
</div>
<div className="card-footer">
<button onClick={openPopup} className="btn btn-secondary">Click To view Samples</button>
</div>
);
}
export default feed;

How to pass data from parent to child in react.js

I have a parent component which has 1 child. I am updating my child by passing data through props. initially, it works fine but when I click on a button and update the state using setState the child gets rendered with old values by the time setState is finished. I have solved it using componentWillReceiveProps in the child but is this the right way?
In the below code if I do setState in filterResults function it won't update the Emplist component .
import React, { Component } from 'react';
import {Search} from './search-bar'
import Emplist from './emplist'
class App extends Component {
constructor(props){
super(props);
this.emp=[{
name:'pawan',
age:12
},
{
name:'manish',
age : 11
}]
this.state={emp:this.emp};
this.filterResults=this.filterResults.bind(this);
}
filterResults(val)
{
if(this.state)
{
let filt=[];
filt.push(
this.emp.find(e=>{
return e.age==val
})
);
this.setState({emp:filt});
}
}
render() {
return (
<div className="App">
<Search filterResults={this.filterResults}/>
<Emplist emp={this.state.emp}/>
</div>
);
}
}
export default App;
EmpList Componet
import React,{Component} from 'react'
export default class Emp extends Component
{
constructor(props){
super(props);
this.emplist=this.props.emp.map(e=>{return <li>{e.name}</li>});
this.next=this.emplist;
}
componentWillReceiveProps(nextProps,nextState,prevProps,prevState,nextContext,prevContext){
// this.props.updated(this.props.empo);
this.next=nextProps.emp[0];
if(this.next)
this.emplist= nextProps.emp.map(e=>{return <li>{e.name}</li>});
}
render(){
if(!this.next)
return <div>name not found</div>
else
return (
<div>
<br/>
<p>The list is here</p>
<ul>
{this.emplist}
</ul>
</div>
)
}
}

If you want to pass from parent to child you can pass using props and if you wan t to do reverse than you can pass one function from parent to child and than use this passed function to send something back to parent.
child will look something like this
class Reciepe extends Component{
render(){
const { title, img, instructions } = this.props;
const ingredients=this.props.ingredients.map((ing,index)=>(<li key={index} >{ing}</li>));
return (
<div className='recipe-card'>
<div className='recipe-card-img'> <img src={img} alt={title}/> </div>
<div className='recipe-card-content'>
<h3 className='recipe-title'>Reciepe {title}</h3>
<ul> {ingredients} </ul>
<h4>Instructions:</h4>
<p>{instructions}</p>
</div>
</div>
)
}
}
parent will look something like this
class RecipeList extends Component{
render(){
return (
<div style={{'display':'flex'}}>
{this.props.recipes.map((item,index)=>(
<Recipe key={index}
title={item.title}
ingredients={item.ingredients}
instructions={item.instructions}
img={item.img}
/>
))}
</div>
)
}
}

The problem is that you are assigning the values to this which is not a good practice. Check where to declare variable in React here.
If you are not using the props to do any complex operations. This should work.
EmpList Componet
import React, {Component} from 'react'
export default class Emp extends Component {
constructor(props) {
super(props);
}
render() {
if (!this.next)
return <div>name not found</div>;
else
return (
<div>
<br/>
<p>The list is here</p>
<ul>
{this.props.emp && this.props.emp.map(e => <li>{e.name}</li>)}
</ul>
</div>
)
}
}

Your next and emplist class properties are directly derivable from your props and hence you don't actually need them. You could do it in the following way
import React,{Component} from 'react'
export default class Emp extends Component{
render(){
const { emp } = this.props;
if(!emp || emp.length === 1)
return <div>name not found</div>
else {
return (
<div>
<br/> <p>The list is here</p>
<ul>
{emp.map(e=>{return <li>{e.name}</li>});}
</ul>
</div>
)
}
}
}
However in cases when you do what to make really complex decisions based on props, a combination of componentWillReceiveProps and componentDidMount/componentWillMount is the right place to do it.

Can I make this React component State-less?

I has not state but it does have logic. A simple mapping. What is the process for making it state-less?
import React from 'react';
import BMFave from './BMFave.jsx';
class BMTag extends React.Component {
constructor(props) {
super(props);
}
render () {
const bookmarks = this.props.bookmarks.map((bookmark) =>
<BMFave bookmark={bookmark} key={bookmark.id} />
);
return (
<div className="bookmark_page" id="{this.props.tag}" >
<div className="bookmark_tag_title">
<p className="bookmark_tag_title_p">
{this.props.tag}
</p>
</div>
{bookmarks}
</div>
)
}
}
export default BMTag;

Stateless doesn't mean no logic, it means no state. So you're already there.
Of course you can simplify:
export default ({bookmarks, tag})=> (
<div className="bookmark_page" id={tag} >
<div className="bookmark_tag_title">
<p className="bookmark_tag_title_p">
{tag}
</p>
</div>
{
bookmarks.map(bm=> <BMFave bookmark={bm} key={bm.id} />)
}
</div>
)

Sure. Just move your mapping function outside the function. You could also leave it in, if you want, but that's not the best practice since it'd get recreated on every render (I think).
import React from 'react';
import BMFave from './BMFave.jsx';
const constructBookmarks = (bookmarks) => {
return bookmarks.map((bookmark) =>
<BMFave bookmark={bookmark} key={bookmark.id} />
);
};
export default (props) => {
return (
<div className="bookmark_page" id={props.tag} >
<div className="bookmark_tag_title">
<p className="bookmark_tag_title_p">
{props.tag}
</p>
</div>
{constructBookmarks(props.bookmarks)}
</div>
);
};

As long as your component does not have a state and does not use React lifecycle methods or refs, it can be a stateless component.
const BMTag = props => {
const bookmarks = props.bookmarks.map((bookmark) =>
<BMFave bookmark={bookmark} key={bookmark.id} />);
return (
<div className="bookmark_page" id="{props.tag}" >
<div className="bookmark_tag_title">
<p className="bookmark_tag_title_p">
{props.tag}
</p>
</div>
{bookmarks}
</div>
)
}
export default BMTag;
For more information, you could check this article about Presentational and Container Components by Dan Abramov.

Filtering List in React

I am creating a basic blog in react using Flux + React Router + Firebase. I am having trouble trying to get a single blog post to render. When I click on the link to a single post, I try to filter out all of the other posts from a list of all posts and display only a single post from my firebase database.
I attempt to do this by matching the key of the firebase entry with the url params like so if (this.props.routeParams.key===key) . I really do not know what I have to do to make this happen. Any suggestions are welcome.
Below is Blogger.jsx, the page where I allow a user to create a blog post and then beneath the blog post, I display a list of the titles all blog posts.
import AltContainer from 'alt-container';
import React from 'react';
import { Link } from 'react-router';
import List from './List.jsx'
import Firebase from 'firebase'
import BlogStore from '../stores/BlogStore'
import BlogActions from '../actions/BlogActions';
const rootURL = 'https://incandescent-fire-6143.firebaseio.com/';
export default class Blogger extends React.Component {
constructor(props) {
super(props);
BlogStore.getState();
BlogStore.mountFirebase();
{console.log(this.props.location.query)}
};
componentDidMount() {
BlogStore.listen((state) => {
this.setState(state)
})
this.firebaseRef = new Firebase(rootURL + 'items/');
}
componentWillMount() {
BlogStore.unlisten((state) => {
this.setState(state)
})
}
renderList = (key) => {
return (
<Link to={`blogshow/${key}`}> <List key={key} blog={this.state.blog[key]} /> </Link>
)
}
handleInputChange = () => {
BlogStore.setState({
title: this.refs.title.value,
text: this.refs.text.value});
}
handleClick = () => {
BlogStore.handleClick();
}
render() {
return (
<div>
<div className="row panel panel-default">
<div className="col-md-8 col-md-offset-2">
<h2>
Create a New Blog Post
</h2>
</div>
</div>
<h2>Blog Title</h2>
<div className="input-group">
<input
ref="title"
value={BlogStore.state.title}
onChange = {this.handleInputChange}
type="text"
className="form-control"/>
<span className="input-group-btn">
</span>
</div>
<h2>Blog Entry</h2>
<div className="input-group">
<textarea
ref="text"
value={BlogStore.state.text}
onChange = {this.handleInputChange}
type="text"
className="form-control"/>
</div>
<div className="blog-submit input-group-btn">
<button onClick={this.handleClick}
className="btn btn-default" type="button">
Publish Blog Post
</button>
</div>
{/*<List blog={this.state.blog} />*/}
{Object.keys(BlogStore.state.blog)
.map(this.renderList)}
</div>
);
}
}
When a user clicks on a link to a single blog post, they should be transported to a page which shows only that single blog post. I have called this component BlogShow. I can't get BlogShow to render because I keep on getting the error
invariant.js?4599:45 Uncaught Invariant Violation: BlogShow.render(): A
valid React element (or null) must be returned. You may have returned
undefined, an array or some other invalid object.
This is BlogShow.jsx:
import AltContainer from 'alt-container';
import React from 'react';
import { Link } from 'react-router';
import Blogger from './Blogger'
import List from './List'
const rootURL = 'https://incandescent-fire-6143.firebaseio.com/';
import BlogStore from '../stores/BlogStore'
import BlogActions from '../actions/BlogActions';
export default class BlogShow extends React.Component {
constructor(props) {
super(props);
{console.log(this.props.routeParams.key)}
this.filterList = this.filterList.bind(this);
}
filterList(key) {
if (this.props.routeParams.key===key) {
return (<List key={key} blog={BlogStore.state.blog[key]} />)
}
}
render() {
<div> {Object.keys(BlogStore.state.blog).map(this.filterList)} </div>
}
}

You are getting that error because your Component BlogShow is not returning anything.
render() {
<div> {Object.keys(BlogStore.state.blog).map(this.filterList)} </div>
}
Should be:
render() {
return <div> {Object.keys(BlogStore.state.blog).map(this.filterList)} </div>
}

I'm not familiar with React.js at all, but I am familiar with pure JS arrays. To remove elements from an array, you should use .filter(), and then afterwards you can map the items.
Something like this:
filterList(key) {
return this.props.routeParams.key === key; // true if the item should stay in the list
}
mapList(key) {
return <List key={key} blog={BlogStore.state.blog[key]} />;
}
render() {
return <div> {Object.keys(BlogStore.state.blog).filter(this.filterList).map(this.mapList)} </div>;
}