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Trying to display one element from an Array -ReactJs

I am trying to make a flashcard web app for language learning and/or rote learning. I have managed to show the first element of the array which contains the data that I'm fetching from the backend but I can't switch from the first element to the subsequent elements.
Here is my code in React:
// Decklist component that displays the flashcard
import { React, useEffect, useState, useContext } from "react";
import Card from "./Card";
import cardContext from "../store/cardContext";
const axios = require("axios");
export default function Decklist() {
//State for data fetched from db
const [data, setData] = useState([]);
//State for array element to be displayed from the "data" state
const [position, setPosition] = useState(0);
//function to change the array element to be displayed after user reads card
const setVisibility = () => {
setPosition(position++);
};
//function to change the difficulty of a card
const difficultyHandler = (difficulty, id) => {
console.log(difficulty);
setData(
data.map((ele) => {
if (ele.ID === id) {
return { ...ele, type: difficulty };
}
return ele;
})
);
};
//useEffect for fetching data from db
useEffect(() => {
axios
.get("/api/cards")
.then((res) => {
if (res.data) {
console.log(res.data);
setData(res.data.sort(() => (Math.random() > 0.5 ? 1 : -1)));
}
})
.catch((err) => {
console.log(err);
});
}, []);
return (
<cardContext.Provider
value={{ cardData: data, setDifficulty: difficultyHandler }}
>
{data.length && (
<Card
position={position}
// dataIndex={index}
visible={setVisibility}
id={data[position].ID}
front={data[position].Front}
back={data[position].Back}
/>
)}
</cardContext.Provider>
);
}
//Card component
import { React, useState, useEffect } from "react";
import Options from "./Options";
export default function Card(props) {
//State for showing or hiding the answer
const [reverse, setReverse] = useState(false);
const [display, setDisplay] = useState(true);
//function for showing the answer
const reversalHandler = () => {
setReverse(true);
};
return (
<div>
{reverse ? (
<div className="card">
{props.front} {props.back}
<button
onClick={() => {
props.visible();
}}
>
Next Card
</button>
</div>
) : (
<div className="card">{props.front}</div>
)}
<Options
visible={props.visible}
reverse={reversalHandler}
id={props.id}
/>
</div>
);
}
//Options Component
import { React, useContext, useState } from "react";
import cardContext from "../store/cardContext";
export default function Options(props) {
const ctx = useContext(cardContext);
const [display, setDisplay] = useState(true);
return (
<>
<div className={display ? "" : "inactive"}>
<button
onClick={() => {
setDisplay(false);
props.reverse();
ctx.setDifficulty("easy", props.id);
}}
>
Easy
</button>
<button
onClick={() => {
setDisplay(false);
props.reverse();
ctx.setDifficulty("medium", props.id);
}}
>
Medium
</button>
<button
onClick={() => {
setDisplay(false);
props.reverse();
ctx.setDifficulty("hard", props.id);
}}
>
Hard
</button>
</div>
</>
);
}
The setVisibility function in the Decklist component is working fine and setting the position state properly. However, I don't know how to re-render the Card component so that it acts on the position state that has changed.

One way to force a re-render of a component is to set its state to itself
onClick={() => {
props.visible();
setReverse(reverse);
}}
However this probably isn't your issue as components will automatically re-render when their state changes or a parent re-renders. This means that for some reason the Card component isn't actually changing the parent component.

Not able to convert react custom hook to be a context

I have a custom hook(useData) that takes query as an argument and then returns data and runtime(time to fetch the data from the API). But I need access to the runtime to my Editor component when I click on the run button. Right now what is happening is when I click on run button(inside Editor.js), it sets the query to the App component using the setter function and then it passes that query to the Table component and then calls the custom hook using that query and then table make use of that data. but I want the runtime in the Editor component, not in the Table component. I know I can call useData hook in the Editor component but my editor component gets rerender every time when we write on the editor, so It calls the useData() hook on each change.
If I create a context using this hook then I can able to access the runtime and data wherever I want.
Anyone, please help me how to convert that to context!
App.js code
import React, { useState } from "react";
import "./assets/output.css";
import Footer from "./components/layouts/Footer";
import Navbar from "./components/layouts/Navbar";
import Sidebar from "./components/layouts/Sidebar";
import TableSection from "./components/table/TableSection";
import Editor from "./components/editor/Editor";
const App = () => {
const [query, setQuery] = useState("");
const [value, setValue] = useState("select * from customers");
return (
<>
<div className="grid grid-cols-layout-desktop grid-rows-layout-desktop bg-gray-600 h-screen">
<Navbar />
<Sidebar setQuery={setQuery} setValue={setValue} />
<Editor setQuery={setQuery} value={value} setValue={setValue} />
{query ? <TableSection query={query} /> : null}
<Footer />
</div>
</>
);
};
export default App;
Editor.js
import React from "react";
import AceEditor from "react-ace";
import "ace-builds/src-min-noconflict/ext-language_tools";
import "ace-builds/src-min-noconflict/mode-mysql";
import "ace-builds/src-noconflict/theme-github";
import useData from "../../hooks/useData";
const Editor = ({ setQuery, value, setValue }) => {
const { runtime } = useData();
const onChange = (newValue) => {
setValue(newValue);
};
const onSubmit = () => {
var Z = value.toLowerCase().slice(value.indexOf("from") + "from".length);
setQuery(Z.split(" ")[1]);
};
return (
<div className="col-start-2 col-end-3 row-start-2 row-end-3 m-6">
<AceEditor
aria-label="query editor input"
mode="mysql"
theme="github"
name={Math.floor(Math.random() * 100000).toString()}
fontSize={16}
minLines={15}
maxLines={10}
width="100%"
showPrintMargin={false}
showGutter
placeholder="Write your Query here..."
editorProps={{ $blockScrolling: true }}
setOptions={{
enableBasicAutocompletion: true,
enableLiveAutocompletion: true,
enableSnippets: true,
}}
value={value}
onChange={onChange}
showLineNumbers
/>
<div className="">
<button
className="bg-white text-gray-800 rounded-md font-semibold px-4 py-2 my-4"
onClick={onSubmit}
>
<i className="fas fa-play"></i> Run SQL
</button>
</div>
</div>
);
};
export default Editor;
Hook code:
import { useEffect, useState } from "react";
import alasql from "alasql";
import toast from "react-hot-toast";
import TABLE_NAMES from "../utils/tableNames";
const getURL = (name) =>
`https://raw.githubusercontent.com/graphql-compose/graphql-compose-examples/master/examples/northwind/data/csv/${name}.csv`;
const useData = (tableName) => {
const [data, setData] = useState([]);
const [error, setError] = useState(false);
const [runtime, setRuntime] = useState("");
const convertToJson = (data) => {
alasql
.promise("SELECT * FROM CSV(?, {headers: false, separator:','})", [data])
.then((data) => {
setData(data);
toast.success("Query run successfully");
})
.catch((e) => {
toast.error(e.message);
});
};
const fetchData = (tableName) => {
setData([]);
const name = TABLE_NAMES.find((name) => name === tableName);
if (name) {
setError(false);
fetch(getURL(tableName))
.then((res) => res.text())
.then((data) => convertToJson(data));
} else {
setError(true);
toast.error("Please enter a valid query");
}
};
useEffect(() => {
let t0 = performance.now(); //start time
fetchData(tableName);
let t1 = performance.now(); //end time
setRuntime(t1 - t0);
console.log(
"Time taken to execute add function:" + (t1 - t0) + " milliseconds"
);
}, [tableName]);
return { data, runtime, error };
};
export default useData;

If you want to create a context and use it wherever you want, you can create a context, and add the state in this component and pass it to the value prop in the Provider component.
See the sample code.
import React, { createContext, useState } from "react";
export const UserContext = createContext({});
export interface User {
uid: string;
email: string;
}
export const UserProvider = ({ children }: any) => {
const [user, setUser] = useState<User>();
// you can defined more hooks at here
return (
// Pass the data to the value prop for sharing data
<UserContext.Provider value={{ user, setUser }}>
{children}
</UserContext.Provider>
);
};
Then wrap components with the provider function like this
<UserProvider>
<MyComponment1>
</MyComponment1>
<MyComponment2>
</MyComponment2>
<MyComponment3>
</MyComponment3>
</UserProvider>
At This time, Whatever Component in the UserProvider can access the context right now and you can use useContext hook to access the data that you pass in the value props
export const MyComponment1 = () => {
const { user, setUser } = useContext<any>(UserContext);
...
}

How do I delete a list item that has been given a unique id when created, in React + Firebase?

I am creating a Todo list using React and Firebase. So far, I have already created the AddToDo functionality, however, now I am having trouble with the delete functionality. I believe this is where my problem lies. For example, when I try and click the delete icon that I set up, I get an error:
Unhandled Runtime Error
TypeError: Cannot read properties of undefined (reading 'id')
This is the code if it helps. AddLink.js
import { useState, useEffect } from "react";
import classes from "./addlink.module.css";
import firebase from "firebase/app";
import initFirebase from "../../config";
import "firebase/firestore";
import Todo from "../Todo/Todo";
import { v4 as uuidv4 } from "uuid";
initFirebase();
const db = firebase.firestore();
function AddLink(props) {
const [todos, setTodos] = useState([]);
const [input, setInput] = useState("");
useEffect(() => {
db.collection("links")
.orderBy("timestamp", "desc")
.onSnapshot((snapshot) => {
// this gives back an array
setTodos(
snapshot.docs.map((doc) => ({
id: doc.id,
todo: doc.data().todo,
}))
);
});
}, []);
const addTodo = (event) => {
event.preventDefault();
console.log("clicked");
db.collection("links").add({
id: uuidv4(),
todo: input,
timestamp: firebase.firestore.FieldValue.serverTimestamp(),
});
setInput("");
};
return (
<div className={classes.addlink}>
<form>
<div className={classes.adminlink}>
<input
type="text"
value={input}
onChange={(event) => setInput(event.target.value)}
/>
<button
className={classes.adminbutton}
type="submit"
onClick={addTodo}
>
Add new link
</button>
</div>
</form>
{todos.map((todo, id) => (
<Todo value={todo} key={id} />
))}
{/* {modalIsOpen && (
<Modal onCancel={closeModalHandler} onConfirm={closeModalHandler} />
)}
{modalIsOpen && <Backdrop onCancel={closeModalHandler} />} */}
</div>
);
}
export default AddLink;
And Todo.js
import React from "react";
import { AiOutlinePicture } from "react-icons/ai";
import { AiOutlineStar } from "react-icons/ai";
import { GoGraph } from "react-icons/go";
import DeleteForeverIcon from "#material-ui/icons/DeleteForever";
import classes from "./todo.module.css";
import firebase from "firebase/app";
import initFirebase from "../../config";
import "firebase/firestore";
initFirebase();
const db = firebase.firestore();
function Todo(props) {
const deleteHandler = () => {
db.collection("todos").doc(props.todo.id).delete();
};
return (
<li className={classes.adminsection}>
<div className={classes.linkCards}>
<h3>{props.text}</h3>
<p>This is a new link</p>
<div>
<AiOutlinePicture />
<AiOutlineStar />
<GoGraph />
<DeleteForeverIcon onClick={deleteHandler} />
</div>
</div>
</li>
);
}
export default Todo;
Any help would be greatly appreciated.

const deleteHandler = () => {
db.collection("todos").doc(props.todo.id).delete();
};
You should replace props.todo.id with props.value.id.
const deleteHandler = () => {
db.collection("todos").doc(props.value.id).delete();
};
Alternatively you can change:
<Todo value={todo} key={id} />
To
<Todo todo={todo} key={id} />
The key you use to access props.value should be the same as the one declared in the jsx template. Using proptypes can help you avoid those mistakes.

After deleting from the database you should update the state, UI with
Todos.filter(d=>d.id !== id of deleted list item)

React API call in useEffect runs only when parameter is hardcoded, not when using state

Hi I am creating an app where a user can search for a book and put it on a shelf depending on which shelf the user clicks on. Currently the user can type a query and many results can get displayed. The user can open a dropdown on a book and click on a shelf (in the dropdown) to select a shelf for that book.
I want to call a method that will update the shelf of a book. It works only if the shelfType is hardcoded however (shelfTypes are 'wantToRead', 'read', 'currentlyReading'). What I want to happen is that the user clicks on a shelf and that shelf is set as the local state variable shelfType in SearchPage. Then once the shelfType changes, the method to update the shelf of a book will run (it makes an API call to a backend).
But for some strange reason I can only update the shelf if I hardcode the shelf type into the update method, not when I use the value of the state shelfType. What am I doing wrong? I hope this question makes sense.
SearchPage.js
import React, { useEffect, useState } from 'react';
import { BsArrowLeftShort } from 'react-icons/bs';
import SearchBar from '../components/SearchBar';
import { search, update, getAll } from '../api/BooksAPI';
import Book from '../components/Book';
const SearchPage = () => {
const [query, setQuery] = useState('');
const [data, setData] = useState([]);
const handleChange = (e) => {
setQuery(e.target.value);
};
useEffect(() => {
const bookSearch = setTimeout(() => {
if (query.length > 0) {
search(query).then((res) => {
if (res.length > 0) {
setData(res);
} else setData([]);
});
} else {
setData([]); // make sure data is not undefined
}
}, 1000);
return () => clearTimeout(bookSearch);
}, [query]);
const [shelfType, setShelfType] = useState('None');
const [currentBook, setCurrentBook] = useState({});
const doSomethingWithBookAndShelf = (book, shelf) => {
setShelfType(shelf);
setCurrentBook(book);
};
useEffect(() => {
//following line doesn't update like this, but I want it to work like this
update(currentBook, shelfType).then((res) => console.log(res));
// update works if I run update(currentBook, 'wantToRead').then((res) => console.log(res));
getAll().then((res) => console.log(res));
}, [shelfType]);
return (
<div>
<SearchBar
type="text"
searchValue={query}
placeholder="Search for a book"
icon={<BsArrowLeftShort />}
handleChange={handleChange}
/>
<div className="book-list">
{data !== []
? data.map((book) => (
<Book
book={book}
key={book.id}
doSomethingWithBookAndShelf={doSomethingWithBookAndShelf}
/>
))
: 'ok'}
</div>
</div>
);
};
export default SearchPage;
Book.js
import React from 'react';
import PropTypes from 'prop-types';
import ButtonDropDown from './ButtonDropDown';
const Book = ({ book, doSomethingWithBookAndShelf }) => {
return (
<div className="book">
<img
src={book.imageLinks.thumbnail}
alt={book.title}
className="book-thumbnail"
/>
<ButtonDropDown
choices={['Currently Reading', 'Want to Read', 'Read', 'None']}
onSelectChoice={(choice) => {
// book came from the component props
doSomethingWithBookAndShelf(book, choice);
}}
/>
<div className="book-title">{book.title}</div>
<div className="book-authors">{book.authors}</div>
</div>
);
};
Book.propTypes = {
doSomethingWithBookAndShelf: PropTypes.func.isRequired,
book: PropTypes.shape({
imageLinks: PropTypes.shape({
thumbnail: PropTypes.string.isRequired,
}),
title: PropTypes.string.isRequired,
authors: PropTypes.arrayOf(PropTypes.string),
}).isRequired,
};
export default Book;
ButtonDropDown.js
import React, { useState } from 'react';
import PropTypes from 'prop-types';
import { BsFillCaretDownFill } from 'react-icons/bs';
const ButtonDropDown = ({ choices, label, onSelectChoice }) => {
const [active, setActive] = useState(false);
const toggleClass = () => {
setActive(!active);
};
return (
<div className="dropdown">
<button
type="button"
className="dropbtn"
onFocus={toggleClass}
onBlur={toggleClass}
>
<BsFillCaretDownFill />
</button>
<div
id="myDropdown"
className={`dropdown-content ${active ? `show` : `hide`}`}
>
<div className="dropdown-label">{label}</div>
{choices.map((choice, index) => (
<button
// eslint-disable-next-line react/no-array-index-key
key={index}
className="dropdown-choice"
onClick={() => {
// we create an specific callback for each item
onSelectChoice(choice);
}}
type="button"
value={choice}
>
{choice}
</button>
))}
</div>
</div>
);
};
ButtonDropDown.propTypes = {
choices: PropTypes.arrayOf(PropTypes.string).isRequired,
label: PropTypes.string,
onSelectChoice: PropTypes.func.isRequired,
};
ButtonDropDown.defaultProps = {
label: 'Move to...',
};
export default ButtonDropDown;

Cause you're "Want to Read" text in choices is different
choices={['Currently Reading', *'Want to Read'*, 'Read', 'None']}
Based on this // update works if I run update(currentBook, 'wantToRead').then((res) => console.log(res));
"wanToRead" is not equal to "Want to Read"

Reducer/Context Api

So I have a Context created with reducer. In reducer I have some logic, that in theory should work. I have Show Component that is iterating the data from data.js and has a button.I also have a windows Component that is iterating the data. Anyway the problem is that when I click on button in Show Component it should remove the item/id of data.js in Windows Component and in Show Component, but when I click on it nothing happens. I would be very grateful if someone could help me. Kind regards
App.js
const App =()=>{
const[isShowlOpen, setIsShowOpen]=React.useState(false)
const Show = useRef(null)
function openShow(){
setIsShowOpen(true)
}
function closeShowl(){
setIsShowOpen(false)
}
const handleShow =(e)=>{
if(show.current&& !showl.current.contains(e.target)){
closeShow()
}
}
useEffect(()=>{
document.addEventListener('click',handleShow)
return () =>{
document.removeEventListener('click', handleShow)
}
},[])
return (
<div>
<div ref={show}>
<img className='taskbar__iconsRight' onClick={() =>
setIsShowOpen(!isShowOpen)}
src="https://winaero.com/blog/wp-content/uploads/2017/07/Control-
-icon.png"/>
{isShowOpen ? <Show closeShow={closeShow} />: null}
</div>
)
}
```Context```
import React, { useState, useContext, useReducer, useEffect } from 'react'
import {windowsIcons} from './data'
import reducer from './reducer'
const AppContext = React.createContext()
const initialState = {
icons: windowsIcons
}
const AppProvider = ({ children }) => {
const [state, dispatch] = useReducer(reducer, initialState)
const remove = (id) => {
dispatch({ type: 'REMOVE', payload: id })
}
return (
<AppContext.Provider
value={{
...state,
remove,
}}
>
{children}
</AppContext.Provider>
)
}
export const useGlobalContext = () => {
return useContext(AppContext)
}
export { AppContext, AppProvider }
reducer.js
const reducer = (state, action) => {
if (action.type === 'REMOVE') {
return {
...state,
icons: state.icons.filter((windowsIcons) => windowsIcons.id !== action.payload),
}
}
}
export default reducer
``data.js```
export const windowsIcons =[
{
id:15,
url:"something/",
name:"yes",
img:"/images/icons/crud.png",
},
{
id:16,
url:"something/",
name:"nine",
img:"/images/icons/stermm.png",
},
{
id:17,
url:"domething/",
name:"ten",
img:"/images/icons/ll.png",
},
{
id:18,
url:"whatever",
name:"twenty",
img:"/images/icons/icons848.png",
},
{
id:19,
url:"hello",
name:"yeaa",
img:"/images/icons/icons8-96.png",
},
]
``` Show Component```
import React from 'react'
import { useGlobalContext } from '../../context'
import WindowsIcons from '../../WindowsIcons/WindowsIcons'
const Show = () => {
const { remove, } = useGlobalContext()
return (
<div className='control'>
{windowsIcons.map((unin)=>{
const { name, img, id} = unin
return (
<li className='control' key ={id}>
<div className='img__text'>
<img className='control__Img' src={img} />
<h4 className='control__name'>{name}</h4>
</div>
<button className='unin__button' onClick={() => remove(id)} >remove</button>
</li> )
</div>
)
}
export default Show
import React from 'react'
import {windowsIcons} from "../data"
import './WindowsIcons.css'
const WindowsIcons = ({id, url, img, name}) => {
return (
<>
{windowsIcons.map((icons)=>{
const {id, name , img ,url} =icons
return(
<div className='windows__icon' >
<li className='windows__list' key={id}>
<a href={url}>
<img className='windows__image' src={img}/>
<h4 className='windows__text'>{name}</h4>
</a>
</li>
</div>
)
})}
</>
)
}

Issue
In the reducer you are setting the initial state to your data list.
This is all correct.
However, then in your Show component you are directly importing windowsIcons and looping over it to render. So you are no longer looping over the state the reducer is handling. If the state changes, you won't see it.
Solution
In your Show component instead loop over the state that you have in the reducer:
const { remove, icons } = useGlobalContext()
{icons.map((unin) => {
// Render stuff
}
Now if you click remove it will modify the internal state and the icons variable will get updated.
Codesandbox working example