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Sometimes when I click the Add button the function is adding an empty array to the JSON file

Sometimes when I click the Add button the function is adding an empty array to the JSON file. But sometimes it works as intended. I've tried moving the variables and state around and it is still doing the same thing. The exercise prop comes from a search of an API and the prop is passed down to this component. The component displays a list of saved exercise cards that can be added to the database. Why is this happening?
import {
Button,
Card,
CardContent,
CardMedia,
Container,
Typography,
} from "#mui/material";
import { Box } from "#mui/system";
import React, { useState } from "react";
const ExerciseCard = ({ exercise }) => {
const [selectedExercise, setSelectedExercise] = useState([]);
const [selectedExerciseName, setSelectedExerciseName] = useState();
const [fetchedData, setFetchedData] = useState([]);
const addExerciseToDB = async () => {
await fetch("http://localhost:3001/savedexercises")
.then((res) => {
return res.json();
})
.then((data) => {
setFetchedData(data);
return fetchedData;
});
const savedFetchedName = fetchedData.map((fetched) => fetched.name);
setSelectedExercise([]);
setSelectedExercise({
apiId: exercise.id,
name: exercise.name,
target: exercise.target,
gifUrl: exercise.gifUrl,
});
setSelectedExerciseName(exercise.name);
if (savedFetchedName.includes(selectedExerciseName)) {
console.log("already added exercise");
} else {
console.log("adding new exercise");
await fetch("http://localhost:3001/savedExercises", {
method: "POST",
body: JSON.stringify(selectedExercise),
headers: { "Content-Type": "application/json" },
});
}
};
return (
<>
<Container maxWidth="xl">
<Box>
<Card>
<CardMedia
component="img"
alt={exercise.name}
image={exercise.gifUrl}
/>
<CardContent sx={{ pb: 2, height: "75px" }}>
<Typography variant="h5" sx={{ pb: 1 }}>
{exercise.name.toUpperCase()}
</Typography>
<Typography variant="body2">
{exercise.target.toUpperCase()}
</Typography>
</CardContent>
<Box>
<Box>
<Button
variant="contained"
color="error"
size="medium"
sx={{ m: 2 }}
onClick={() => addExerciseToDB()}
>
Add
</Button>
</Box>
</Box>
</Card>
</Box>
</Container>
</>
);
};
export default ExerciseCard;
await fetch("http://localhost:3001/savedexercises")
.then((res) => {
return res.json();
})
.then((data) => {
setFetchedData(data);
return fetchedData;
});

How to handle null state exception for map in reactJs

I have this code which his basic todo list that I am trying to build in react
const Home = (props) => {
const classes = useStyles();
const [addNewTask, setAddNewTask] = useState(false);
const [formData, setFormData] = React.useState({ taskText: "" });
const dispatch = useDispatch();
useEffect(() => {
dispatch(getTasks());
}, [dispatch]);
const todos = useSelector((state) => state.todos);
const handleAddNew = () => {
setAddNewTask(addNewTask ? false : true);
};
const handleChange = (e) => {
setFormData({ ...formData, [e.target.name]: e.target.value });
};
const handleSubmit = (e) => {
e.preventDefault();
console.log(formData);
dispatch(createTask(formData));
dispatch(getTasks())
};
return (
<Grow in>
<Container>
<Grid
className={classes.adjustTop}
container
justify="space-between"
alignItems="stretch"
spacing={3}
>
<Grid item xs={2} sm={2}></Grid>
<Grid item xs={8} sm={8}>
<Typography variant="h2">TODO LIST</Typography>
{todos==null?
<Typography>Loading...</Typography>
:
<>
{todos?.tasks?.map((todo) => (
<Task id={todo.task} todo={todo} />
))}
</>
}
<div style={{ textAlign: "center" }}>
{addNewTask ? (
<>
<Button
variant="contained"
size="large"
color="error"
style={{ marginTop: "10px" }}
onClick={handleAddNew}
>
Cancel Adding task
</Button>
<form style={{ paddingTop: "20px" }} onSubmit={handleSubmit}>
<Input
name="taskText"
label="Task Text"
handleChange={handleChange}
type="text"
placeholder="text"
/>
<br />
<Button type="submit">Submit</Button>
</form>
</>
) : (
<Button
variant="contained"
size="large"
color="primary"
style={{ marginTop: "10px" }}
onClick={handleAddNew}
>
+ Add new task
</Button>
)}
</div>
</Grid>
<Grid item xs={2} sm={2}></Grid>
</Grid>
</Container>
</Grow>
);
};
export default Home;
This is the reducer
import { FETCH_ALL,CREATE } from '../constants/actionTypes';
export default (state = {tasks:null}, action) => {
switch (action.type) {
case FETCH_ALL:
return {...state,tasks:action.payload,errors:null}
case CREATE:
return {...state,tasks:action.payload,errors:null}
default:
return state;
}
};
& actions
import { FETCH_ALL,CREATE} from '../constants/actionTypes';
import * as api from '../api/index.js';
export const getTasks = () => async (dispatch) => {
try {
const { data } = await api.fetchTasks();
console.log(data);
dispatch({ type: FETCH_ALL, payload: data });
} catch (error) {
console.log(error.message);
}
};
export const createTask = (taskText) => async (dispatch) => {
try {
const { data } = await api.createTask(taskText);
dispatch({type:CREATE,payload:data})
} catch (error) {
console.log(error.message);
}
};
I am able to add the data to database on submit using handleSubmit tot the database but the issue is after each submit its giving me an error TypeError: _todos$tasks.map is not a function
I tried to handle this by using ternary operator & rendering Loading text on null & also have used chaining operator,but still getting same error

You are trying to get todos from your redux store
const todos = useSelector((state) => state.todos);
But there is no todos in your state and plus you are updating another state tasks in your reducer:
export default (state = {tasks:null}, action) => {
switch (action.type) {
case FETCH_ALL:
return {...state,tasks:action.payload,errors:null}
case CREATE:
return {...state,tasks:action.payload,errors:null}
default:
return state;
}
};

Context API not displaying array of data

I'm receiving the error 'expected an assignment of function call and instead saw an expression.
*The above error is resolved, it's now giving me an Unhandled Rejection (TypeError): render is not a function. It functions properly until I go to the products page and then gives me the error.
I console logged it and it was pulling the information but then it breaks when I import the ProductBrowse component to display the information.
ProductPage:
class ProductPage extends React.Component {
state = {
shoppingCartOpen: false,
};
drawerToggleClickHandler = () => {
this.setState((prevState) => {
return { shoppingCartOpen: !prevState.shoppingCartOpen };
});
};
render() {
let shoppingCartDrawer;
if (this.state.shoppingCartOpen) {
shoppingCartDrawer = <ShoppingCartDrawer />;
}
return (
<ProductStyling>
<ButtonAppBar drawerClickHandler={this.drawerToggleClickHandler} />
<H1>Products</H1>
{shoppingCartDrawer}
<ProductConsumer>
<Grid container spacing={3}>
{(value) => {
return value.products.map((prod, idx) => {
return (
<Grid item xs={3} key={`${prod.name}-${prod.store}-${idx}`}>
<ProductBrowse
productName={prod.name}
productDesc={prod.desc}
productImg={prod.img}
productPrice={prod.price}
/>
</Grid>
);
});
}}
</Grid>
</ProductConsumer>
;
</ProductStyling>
);
}
}
Structure of value:
const ProductContext = React.createContext();
class ProductProvider extends React.Component {
state = {
products: productData,
};
addToCart = () => {
console.log('Hello from add to cart'); };
render() {
return (
<ProductContext.Provider
value={{ ...this.state, addToCart: this.addToCart }}
>
{this.props.children}
</ProductContext.Provider>
);
}
}
const ProductConsumer = ProductContext.Consumer;
export { ProductProvider, ProductConsumer };
ProductBrowse:
const ProductBrowse = ({
productName,
productDesc,
productImg,
productPrice,
}) => {
const classes = useStyles();
const [open, setOpen] = React.useState(false);
const openModal = () => {
setOpen(!open);
};
const closeModal = () => {
setOpen(!open);
};
return (
<Box border={1} borderRadius={3}>
<Card className={classes.root}>
<CardActionArea onClick={() => openModal()}>
<ProductModal
open={open}
onClick={() => openModal()}
onClose={() => closeModal()}
onSave={() => closeModal()}
productName={productName}
productDesc={productDesc}
/>
<CardHeader
title={productName}
subheader={formatCurrency(productPrice)}
/>
<CardMedia
className={classes.media}
image={productImg}
alt={productDesc}
/>
<CardContent>
<Typography variant='body2' color='textSecondary' component='p'>
{productDesc}
</Typography>
</CardContent>
</CardActionArea>
<CardActions>
<Button size='small' /*To Checkout*/>BUY NOW</Button>
<Button size='small'>ADD TO CART</Button>
<Button size='small'>REVIEW</Button>
</CardActions>
</Card>
</Box>
);
};
ProductData:
import desk from '../../../assets/img/desk.webp';
export const productData = [
{
img: desk,
name: 'Desk',
store: 'Local Furniture Shop 1',
price: 9.99,
desc: "This sturdy desk is built to outlast years of coffee and hard work. You get a generous work surface and a clever solution to keep cords in place underneath."
},
Index.js:
ReactDOM.render(
<React.StrictMode>
<Auth0Provider
domain={auth0Domain}
client_id={auth0ClientID}
redirect_uri={window.location.origin}
onRedirectCallback={onRedirectCallback}
audience={auth0Audience}
scope={"read:current_user"}
>
<ProductProvider>
<Provider store={store}>
<App />
</Provider>
</ProductProvider>
</Auth0Provider>
</React.StrictMode>,
document.getElementById('root')
);

You are not returning anything from ProductConsumer You need to do like this:
<ProductConsumer>
<Grid container spacing={3}>
{(value) => {
return value.products.map((prod, idx) => {
return (
<Grid item xs={3} key={`${prod.name}-${prod.store}-${idx}`}>
<ProductBrowse
productName={prod.name}
productDesc={prod.desc}
productImg={prod.img}
productPrice={prod.price}
/>
</Grid>
);
});
}}
</Grid>
</ProductConsumer>;

ReactJS: Rendering the state separately and not as an array

I ended up pulling off what I wanted. However, it's giving me an array of the state instead of rendering each one separately. This is probably very simple and I'm more than likely over-complicating it but hey, any help would be nice.
Here's what I currently am dealing with
And here's a better example: https://i.imgur.com/WLDkbOb.gif
And lastly here's probably the best overview: https://imgur.com/a/zintqTA
constructor(props) {
super(props);
this.state = {
data: [],
loading: false,
}
}
ws = new WebSocket(URL)
componentDidMount() {
this.ws.onopen = () => {
console.log('connected')
}
this.ws.onmessage = e => {
const tbox = JSON.parse(e.data);
if(tbox.data && tbox.data.length > 0){
this.setState({
data : this.state.data.concat(tbox.data[0]),
})
}
}
this.ws.onclose = () => {
console.log('disconnected')
this.setState({
ws: new WebSocket(URL),
})
}
}
render() {
let { data } = this.state;
const chatBox = data.map(item => {
return (
<List
key={item.id}
dataSource={this.state.data}
renderItem={item => (
<List.Item >
<List.Item.Meta
avatar={<Avatar size="large" icon="user" />}
title={<div>{item.user} {item.date}</div>}
description={item.message}
/>
</List.Item>
)}
>
</List>
)
})
return (
<div>
<div>
{chatBox}
</div>
I'm trying to loop through the state and render each message separately

I think you don't need to loop through this.state.data[] because you are already setting data source to antd <List> component. antd List component handles collection of objects for us.
This would be the code for rendring your this.state.data:
const chatBox = <List dataSource={this.state.data}
renderItem={item => (
<List.Item >
<List.Item.Meta
avatar={<Avatar size="large" icon="user" />}
title={<div>{item.user}
{item.date}</div>}
description={item.message}
/>
</List.Item>
)}
>
</List>;
you can have a look at these links :
https://stackblitz.com/run
https://ant.design/components/list/

How to call child component method from parent

In my Reactjs app, I need to have a parent component (a wizard) named Wizard.js and a number of child components (steps of the wizard) named PrimaryForm.js, SecondaryForm.js etc. They all are Class based components with some local validation functions.
Previous and Next buttons to advance the steps, reside in the Wizard.js.
To advance the next step of the wizard, I'm trying to call a method from PrimaryForm. I checked similar questions in Stackoverflow; tried using ref or forwardRef, but I could not make it work. I currently receive "TypeError: Cannot read property 'handleCheckServer' of null" error.
Below are my parent and child classes. Any help about what I would be doing wrong is appreciated.
Wizard.js:
import React, { Component } from 'react';
...
const getSteps = () => {
return [
'Info',
'Source Details',
'Target Details',
'Configuration'
];
}
class Wizard extends Component {
constructor(props) {
super(props);
this.firstRef = React.createRef();
this.handleNext = this.handleNext.bind(this);
this.state = {
activeStep: 1,
}
}
componentDidMount() {}
handleNext = () => {
if (this.state.activeStep === 1) {
this.firstRef.current.handleCheckServer(); <<<<<<<<<<<<<<<<< This is where I try to call child method
}
this.setState(state => ({
activeStep: state.activeStep + 1,
}));
};
handleBack = () => {
this.setState(state => ({
activeStep: state.activeStep - 1,
}));
};
handleReset = () => {
this.setState({
activeStep: 0,
});
};
render() {
const steps = getSteps();
const currentPath = this.props.location.pathname;
const { classes } = this.props;
return (
<React.Fragment>
<CssBaseline />
<Topbar currentPath={currentPath} />
<div className={classes.root}>
<Grid container spacing={2} justify="center" direction="row">
<Grid container spacing={2} className={classes.grid} justify="center" direction="row">
<Grid item xs={12}>
<div className={classes.topBar}>
<div className={classes.block}>
<Typography variant="h6" gutterBottom>Wizard</Typography>
<Typography variant="body1">Follow the wizard steps to create a configuration.</Typography>
</div>
</div>
</Grid>
</Grid>
<Grid container spacing={2} alignItems="center" justify="center" className={classes.grid}>
<Grid item xs={12}>
<div className={classes.stepContainer}>
<div className={classes.bigContainer}>
<Stepper classes={{ root: classes.stepper }} activeStep={this.state.activeStep} alternativeLabel>
{steps.map(label => {
return (
<Step key={label}>
<StepLabel>{label}</StepLabel>
</Step>
);
})}
</Stepper>
</div>
<PrimaryForm ref={this.firstRef} />
</div>
</Grid>
</Grid>
<Grid container spacing={2} className={classes.grid}>
<Grid item xs={12}>
<div className={classes.flexBar}>
<Tooltip title="Back to previous step">
<div>
<Button variant="contained"
disabled={(this.state.activeStep === 0)}
className={classes.actionButton}
onClick={this.handleBack}
size='large'>
<BackIcon className={classes.rightIcon} />Back
</Button>
</div>
</Tooltip>
<Tooltip title="Proceed the next step">
<div>
<Button
variant="contained" className={classes.actionButton}
color="primary"
size='large'
disabled={!(!this.state.isFormValid || this.state.isTestWaiting)}
onClick={this.handleNext}>
<ForwardIcon className={this.props.classes.rightIcon}/>Next</Button>
</div>
</Tooltip>
<Tooltip title="Cancel creating new configuration">
<Button variant="contained" color="default" className={classes.actionButton}
component={Link} to={'/configs'} style={{ marginLeft: 'auto' }}>
<CancelIcon className={classes.rightIcon} />Cancel
</Button>
</Tooltip>
</div>
</Grid>
</Grid>
</Grid>
</div>
</React.Fragment>
)
}
}
export default withRouter(withStyles(styles)(Wizard));
PrimaryForm.js:
import React, { Component } from 'react';
...
class PrimaryForm extends Component {
constructor(props) {
super(props);
this.handleCheckServer = this.handleCheckServer.bind(this);
this.state = {
hostname: {
value: "localhost",
isError: false,
errorText: "",
},
serverIp: {
value: "127.0.0.1",
isError: false,
errorText: "",
},
isFormValid: true,
isTestValid: true,
testErrorMessage: "",
isTestWaiting: false,
};
}
componentDidMount() { }
handleCheckServer() {
alert('Alert from Child. Server check will be done here');
}
evaluateFormValid = (prevState) => {
return ((prevState.hostname.value !== "" && !prevState.hostname.isError) &&
(prevState.serverIp.value !== "" && !prevState.serverIp.isError));
};
handleChange = event => {
var valResult;
switch (event.target.id) {
case 'hostname':
valResult = PrimaryFormValidator.validateHostname(event.target.value, event.target.labels[0].textContent);
this.setState({
...this.state,
hostname:
{
value: event.target.value,
isError: valResult.isError,
errorText: valResult.errorText,
},
});
break;
case 'serverIp':
valResult = PrimaryFormValidator.validateIpAddress(event.target.value, event.target.labels[0].textContent);
this.setState({
...this.state,
serverIp:
{
value: event.target.value,
isError: valResult.isError,
errorText: valResult.errorText,
}
});
break;
default:
}
this.setState(prevState => ({
...prevState,
isFormValid: this.evaluateFormValid(prevState),
}));
}
render() {
const { classes } = this.props;
return (
<React.Fragment>
<div className={classes.bigContainer}>
<Paper className={classes.paper}>
<div>
<div>
<Typography variant="subtitle1" gutterBottom className={classes.subtitle1} color='secondary'>
Primary System
</Typography>
<Typography variant="body1" gutterBottom>
Information related with the primary system.
</Typography>
</div>
<div className={classes.bigContainer}>
<form className={classes.formArea}>
<TextField className={classes.formControl}
id="hostname"
label="FQDN Hostname *"
onChange={this.handleChange}
value={this.state.hostname.value}
error={this.state.hostname.isError}
helperText={this.state.hostname.errorText}
variant="outlined" autoComplete="off" />
<TextField className={classes.formControl}
id="serverIp"
label="Server Ip Address *"
onChange={this.handleChange}
value={this.state.serverIp.value}
error={this.state.serverIp.isError}
helperText={this.state.serverIp.errorText}
variant="outlined" autoComplete="off" />
</form>
</div>
</div>
</Paper>
</div>
</React.Fragment>
)
}
}
export default withRouter(withStyles(styles)(PrimaryForm));
(ps: I would like to solve this without another framework like Redux, etc if possible)

Example in Typescript.
The idea is that the parent passes its callback to the child. The child calls the parent's callback supplying its own e.g. child callback as the argument. The parent stores what it got (child callback) in a class member variable and calls it later.
import * as React from 'react'
interface ICallback {
(num: number): string
}
type ChildProps = {
parent_callback: (f: ICallback) => void;
}
class Child extends React.Component {
constructor(props: ChildProps) {
super(props);
props.parent_callback(this.childCallback);
}
childCallback: ICallback = (num: number) => {
if (num == 5) return "hello";
return "bye";
}
render() {
return (
<>
<div>Child</div>
</>
)
}
}
class Parent extends React.Component {
readonly state = { msg: "<not yet set>" };
letChildRegisterItsCallback = (fun: ICallback) => {
this.m_ChildCallback = fun;
}
callChildCallback() {
const str = this.m_ChildCallback? this.m_ChildCallback(5) : "<callback not set>";
console.log("Child callback returned string: " + str);
return str;
}
componentDidMount() {
this.setState((prevState) => { return {...prevState, msg: this.callChildCallback()} });
}
render() {
return (
<>
<Child {...{ parent_callback: this.letChildRegisterItsCallback }} />
<div>{this.state.msg}</div>
</>
)
}
m_ChildCallback: ICallback | undefined = undefined;
}
P.S.
The same code in Javascript. The only difference is that interface, type, readonly and type annotations are taken out. Pasting into here confirms it's a valid ES2015 stage-2 code.
class Child extends React.Component {
constructor(props) {
super(props);
props.parent_callback(this.childCallback);
}
childCallback = (num) => {
if (num == 5) return "hello";
return "bye";
}
render() {
return (
<>
<div>Child</div>
</>
)
}
}
class Parent extends React.Component {
state = { msg: "<not yet set>" };
letChildRegisterItsCallback = (fun) => {
this.m_ChildCallback = fun;
}
callChildCallback() {
const str = this.m_ChildCallback? this.m_ChildCallback(5) : "<callback not set>";
console.log("Child callback returned string: " + str);
return str;
}
componentDidMount() {
this.setState((prevState) => { return {...prevState, msg: this.callChildCallback()} });
}
render() {
return (
<>
<Child {...{ parent_callback: this.letChildRegisterItsCallback }} />
<div>{this.state.msg}</div>
</>
)
}
m_ChildCallback = undefined;
}