How to get the number of checked checkboxes in React.js? - javascript

I started learning React not so long ago. Decided to make some kind of "life checklist" as one of my beginner projects. I have been using Functional Components in the core.
FYI:
I have data.js as an array of objects where "action", "emoji" and unique ID are stored.
I import it into my App.js.
const App = () => {
//Looping over data
const items = data.map((item) => {
return (
<ChecklistItem action={item.action} emoji={item.emoji} key={item.id} />
);
});
return (
<>
<GlobalStyle />
<StyledHeading>Life Checklist</StyledHeading>
<StyledApp>{items}</StyledApp>
<h2>Overall number: {data.length}</h2>
</>
);
};
export default App;
Here is my <ChecklistItem/> component:
const ChecklistItem = ({ action, emoji }) => {
//State
const [isActive, setIsActive] = useState(false);
//Event Handlers
const changeHandler = () => {
setIsActive(!isActive);
};
return (
<StyledChecklistItem isActive={isActive}>
<input type="checkbox" checked={isActive} onChange={changeHandler} />
<StyledEmoji role="img">{emoji}</StyledEmoji>
<StyledCaption>{action}</StyledCaption>
</StyledChecklistItem>
);
};
export default ChecklistItem;
I would be satisfied with the functionality so far, but I need to show how many "active" checklist items were chosen in the parent <App/> component like "You have chosen X items out of {data.length}. How can I achieve this?
I assume that I need to lift the state up, but cannot understand how to implement this properly yet.

You can do that by simply creating a state for storing this particular count of active items.
To do that, you would need to update your <App/> component to something like this
const App = () => {
const [activeItemsCount, setActiveItemsCount] = useState(0);
//Looping over data
const items = data.map((item, index) => {
return (
<ChecklistItem
key={index}
action={item.action}
emoji={item.emoji}
setActiveItemsCount={setActiveItemsCount}
/>
);
});
return (
<>
<h1>Life Checklist</h1>
<div>{items}</div>
<div>Active {activeItemsCount} </div>
<h2>Overall number: {data.length}</h2>
</>
);
};
export default App;
And then in your <ChecklistItem /> component, you would need to accept that setActiveItemsCount function so that you can change the state of the activeItemsCount.
import React, { useState, useEffect } from "react";
const ChecklistItem = ({ action, emoji, setActiveItemsCount }) => {
const [isActive, setIsActive] = useState(false);
const changeHandler = () => {
setIsActive(!isActive);
};
useEffect(() => {
if (!isActive) {
setActiveItemsCount((prevCount) => {
if (prevCount !== 0) {
return prevCount - 1;
}
return prevCount;
});
}
if (isActive) {
setActiveItemsCount((prevCount) => prevCount + 1);
}
}, [isActive, setActiveItemsCount]);
return <input type="checkbox" checked={isActive} onChange={changeHandler} />;
};
export default ChecklistItem;
By using the useEffect and the checks for isActive and 0 value, you can nicely increment or decrement the active count number by pressing the checkboxes.

How about this?
const data = [
{ action: '1', emoji: '1', id: 1 },
{ action: '2', emoji: '2', id: 2 },
{ action: '3', emoji: '3', id: 3 },
];
const ChecklistItem = ({ action, emoji, isActive, changeHandler }) => {
return (
<div isActive={isActive}>
<input type="checkbox" checked={isActive} onChange={changeHandler} />
<div>{emoji}</div>
<div>{action}</div>
</div>
);
};
const PageContainer = () => {
const [checkedItemIds, setCheckedItemIds] = useState([]);
function changeHandler(itemId) {
if (checkedItemIds.indexOf(itemId) > -1) {
setCheckedItemIds((prev) => prev.filter((i) => i !== itemId));
} else {
setCheckedItemIds((prev) => [...prev, itemId]);
}
}
const items = data.map((item) => {
const isActive = checkedItemIds.indexOf(item.id) > -1;
return (
<ChecklistItem
isActive={isActive}
changeHandler={() => changeHandler(item.id)}
action={item.action}
emoji={item.emoji}
key={item.id}
/>
);
});
return (
<div className="bg-gray-100">
<div>{items}</div>
<h2>
You have chosen {checkedItemIds.length} items out of {data.length}
</h2>
</div>
);
};

When data is used by a child component, but the parent needs to be aware of it for various reasons, that should be state in the parent component. That state is then handed to the child as props.
One way to do this would be to initialize your parent component with a piece of state that was an array of boolean values all initialized to false. Map that state into the checkbox components themselves and hand isActive as a prop based on that boolean value. You should then also hand the children a function of the parent that will change the state of the boolean value at a certain index of that array.
Here's a bit of a contrived example:
// Parent.tsx
const [checkBoxes, setCheckboxes] = useState(data.map(data => ({
id: data.id,
action: data.action,
emoji: data.emoji
isActive: false,
})));
const handleCheckedChange = (i) => {
setCheckboxes(checkBoxes => {
checkBoxes[i].isActive = !checkBoxes[i].isActive;
return checkBoxes;
})
}
return(
checkBoxes.map((item, i) =>
<ChecklistItem
action={item.action}
emoji={item.emoji}
key={item.id}
index={i}
isActive={item.isActive}
handleChange={handleCheckedChange}
/>
)
);
// CheckListItem.tsx
const CheckListItem = ({ action, emoji, index, isActive, handleChange }) => (
<StyledChecklistItem isActive={isActive}>
<input type="checkbox" checked={isActive} onChange={() => handleChange(index)} />
<StyledEmoji role="img">{emoji}</StyledEmoji>
<StyledCaption>{action}</StyledCaption>
</StyledChecklistItem>
)

Related

React: saving state of child component triggered by parent component

Is there a way to do this?
I want to save a ChildComponent's state into an array state from the GrandParentComponent whenever I click a button from the ParentComponent?
Here's an overview of my components:
const GrandParentComponent = () => {
const [array, setArray] = useState([]);
return (
<div>
<ParentComponent array={array} setArray={setArray} />
</div>
);
};
const ParentComponent = ({ array, setArray }) => {
const ref = useRef(null);
const handleClick = () => {
ref.current.setArray();
};
return (
<div>
<button onClick={handleClick}>save</button>
{array.map((item) => (
<ChildComponent array={array} setArray={setArray} ref={ref} />
))}
</div>
);
};
const ChildComponent = forwardRef(({ array, setArray }, ref) => {
const [childState, setChildState] = useState("")
useImperativeHandle(ref, () => {
return {
setArray: () => {
setArray((array) => [{ ...childState }, ...array]);
}
};
});
return <div>ChildComponent</div>;
});
The problem I'm encountering is it only saves the value of the last ChildComponent. What I want is to save all of the values from the ChildComponents.
What am I doing it wrong here? Or is there a better or correct way of doing what I'm trying to do?

How to disable a react component (or onClick itself) with onClick event

I have seen similar questions but none of the answers are working in my case and I hope someone will be able to tell me why.
My ReactApp renders 3 card components that flip when clicked on. The cards are populated with data from an object array and is rendered with a map function (added info in case it has an impact). Here is parent component.
import React from 'react'
import FlipCard from './FlipCard'
const cards = [
{
id: 1,
text: 'NOPE',
},
{
id: 2,
text: '!!WINNER!!',
},
{
id: 3,
text: 'NOPE',
},
]
const shuffleCards = array => {
for (let i = array.length - 1; i > 0; i--) {
const j = Math.floor(Math.random() * (i + 1))
const temp = array[i]
array[i] = array[j]
array[j] = temp
}
return array
}
shuffleCards(cards)
console.log(cards)
const CardGameUI = () => {
shuffleCards(cards)
return (
<div className="cards-ui">
{cards.map(card => (
<FlipCard key={card.id} text={card.text} value={card.id} />
))}
</div>
)
}
export default CardGameUI
When one of the cards are flipped, I need the onClick for the other cards to be disabled. I tried using state and a conditional in my onClick event but it has no effect. The according to the console.log, the state of the play boolean is changed and if I manually change the conditional in the onCLick event check if play is true, then it works perfectly fine. I am clearly missing something because it seems as though the conditional is working and the state is changing.
import React, { useState } from 'react'
import ReactCardFlip from 'react-card-flip'
import FrontComponent from './FrontComponent'
import BackComponent from './BackComponent'
const FlipCard = ({ text, value }) => {
const [isFlipped, setIsFlipped] = useState(false)
const [activeCard, setActiveCard] = useState(2)
const [play, setPlay] = useState(false)
console.log(play.valueOf())
function handleFlip() {
setPlay(true)
setIsFlipped(!isFlipped)
console.log(isFlipped)
setActiveCard(value)
console.log(value)
}
if (activeCard !== 2) {
console.log('Play again?')
}
return (
<>
<ReactCardFlip isFlipped={isFlipped} flipDirection="horizontal">
<FrontComponent onClick={!play ? handleFlip : null} />
<BackComponent text={text} value={value} />
</ReactCardFlip>
</>
)
}
export default FlipCard
What am I missing?
You should manage the onClick event and the flip state on the parent instead of inside the card.
An high-level overview will be:
const CardGameUI = () => {
const [flipped, setFlipped] = useState({});
const hasFlipped = Object.values(flipped).includes(true);
const handleFlip = id => () => setFlipped(flipped => ({
...flipped,
[id]: true // can be changed to toggle in case you need it in the future
}));
return (
<div>
{cards.map(({ id, text }) => (
<FlipCard
key={id}
text={text}
value={id}
onFlip={handleFlip(id)}
flipped={flipped[id]}
disabled={hasFlipped}
/>
))}
</div>
)
};
const FlipCard = ({ text, value, onFlip, flipped , disabled}) => {
return (
<ReactCardFlip isFlipped={flipped} flipDirection="horizontal">
<FrontComponent onClick={onFlip} disabled={disabled} />
<BackComponent text={text} value={value} />
</ReactCardFlip>
)
}

Handling an indetermined amount of states for n checkboxes in React

I have this solution for handling a fix number of states for a fix number of checkboxes:
import { useState } from 'react';
function App() {
const [arrValues, setArrValues] = useState(
// use a function here to only create the initial array on mount
() => Array.from(
{ length: 10 }
)
);
const setcheckBoxValue = (i) => {
setArrValues(
arrValues.map((v, j) => j !== i ? v : !v)
);
console.log(arrValues);
}
return (
<div className="App">
{arrValues.map( (val, i) =>
<input
key={i}
type="checkbox"
checked={val}
onChange={() => setcheckBoxValue(i)}
>
</input>)
}
</div>
);
}
export default App;
In the code it is 10, but, what if the length of the array is not known until I read some value in a database,
Rafael
You can do something like this. The example below is using an object rather than an array, but this is just example. Also, the “initialValues” could be easily generated from data (from database). These could be the undetermined values you mentioned.
const MyTest = () => {
const initialValues = {
values: { checkbox1: true, checkbox2: false, checkbox3: true }
}
const [state, setState] = useState(initialValues || {})
const handleChange = (event) => {
const target = event.target
const value = target.checked
const name = target.name
setState((prevState) => ({
values: {
...prevState.values,
[name]: value
}
}))
}
return (
<div>
<pre>{JSON.stringify(state, null, 2)}</pre>
{state.values &&
Object.keys(state.values).map((checkboxKey, i) => (
<input
name={checkboxKey}
key={i}
type="checkbox"
checked={state.values[checkboxKey]}
onChange={handleChange}
/>
))}
</div>
)
}

Couldn't correctly initialize state in parent component from children states

I have two React components, namely, Form and SimpleCheckbox.
SimpleCheckbox uses some of the Material UI components but I believe they are irrelevant to my question.
In the Form, useEffect calls api.getCategoryNames() which resolves to an array of categories, e.g, ['Information', 'Investigation', 'Transaction', 'Pain'].
My goal is to access checkboxes' states(checked or not) in the parent component(Form). I have taken the approach suggested in this question.(See the verified answer)
Interestingly, when I log the checks it gives(after api call resolves):
{Pain: false}
What I expect is:
{
Information: false,
Investigation: false,
Transaction: false,
Pain: false,
}
Further More, checks state updates correctly when I click into checkboxes. For example, let's say I have checked Information and Investigation boxes, check becomes the following:
{
Pain: false,
Information: true,
Investigation: true,
}
Here is the components:
const Form = () => {
const [checks, setChecks] = useState({});
const [categories, setCategories] = useState([]);
const handleCheckChange = (isChecked, category) => {
setChecks({ ...checks, [category]: isChecked });
}
useEffect(() => {
api
.getCategoryNames()
.then((_categories) => {
setCategories(_categories);
})
.catch((error) => {
console.log(error);
});
}, []);
return (
{categories.map(category => {
<SimpleCheckbox
label={category}
onCheck={handleCheckChange}
key={category}
id={category}
/>
}
)
}
const SimpleCheckbox = ({ onCheck, label, id }) => {
const [check, setCheck] = useState(false);
const handleChange = (event) => {
setCheck(event.target.checked);
};
useEffect(() => {
onCheck(check, id);
}, [check]);
return (
<FormControl>
<FormControlLabel
control={
<Checkbox checked={check} onChange={handleChange} color="primary" />
}
label={label}
/>
</FormControl>
);
}
What I was missing was using functional updates in setChecks. Hooks API Reference says that: If the new state is computed using the previous state, you can pass a function to setState.
So after changing:
const handleCheckChange = (isChecked, category) => {
setChecks({ ...checks, [category]: isChecked });
}
to
const handleCheckChange = (isChecked, category) => {
setChecks(prevChecks => { ...prevChecks, [category]: isChecked });
}
It has started to work as I expected.
It looks like you're controlling state twice, at the form level and at the checkbox component level.
I eliminated one of those states and change handlers. In addition, I set checks to have an initialState so that you don't get an uncontrolled to controlled input warning
import React, { useState, useEffect } from "react";
import { FormControl, FormControlLabel, Checkbox } from "#material-ui/core";
import "./styles.css";
export default function App() {
return (
<div className="App">
<h1>Hello CodeSandbox</h1>
<Form />
</div>
);
}
const Form = () => {
const [checks, setChecks] = useState({
Information: false,
Investigation: false,
Transaction: false,
Pain: false
});
const [categories, setCategories] = useState([]);
console.log("checks", checks);
console.log("categories", categories);
const handleCheckChange = (isChecked, category) => {
setChecks({ ...checks, [category]: isChecked });
};
useEffect(() => {
// api
// .getCategoryNames()
// .then(_categories => {
// setCategories(_categories);
// })
// .catch(error => {
// console.log(error);
// });
setCategories(["Information", "Investigation", "Transaction", "Pain"]);
}, []);
return (
<>
{categories.map(category => (
<SimpleCheckbox
label={category}
onCheck={handleCheckChange}
key={category}
id={category}
check={checks[category]}
/>
))}
</>
);
};
const SimpleCheckbox = ({ onCheck, label, check }) => {
return (
<FormControl>
<FormControlLabel
control={
<Checkbox
checked={check}
onChange={() => onCheck(!check, label)}
color="primary"
/>
}
label={label}
/>
</FormControl>
);
};
If you expect checks to by dynamically served by an api you can write a fetchHandler that awaits the results of the api and updates both slices of state
const fetchChecks = async () => {
let categoriesFromAPI = ["Information", "Investigation", "Transaction", "Pain"] // api result needs await
setCategories(categoriesFromAPI);
let initialChecks = categoriesFromAPI.reduce((acc, cur) => {
acc[cur] = false
return acc
}, {})
setChecks(initialChecks)
}
useEffect(() => {
fetchChecks()
}, []);
I hardcoded the categoriesFromApi variable, make sure you add await in front of your api call statement.
let categoriesFromApi = await axios.get(url)
Lastly, set your initial slice of state to an empty object
const [checks, setChecks] = useState({});

How do I update a single item in list with React Context?

I really like react context, but I think it's missing something (or maybe I don't know how to do it)
Say I have a list of todos and it's corresponding provider as
const Home = () => (
<div className="container">
<TodosProvider>
<TodosList />
</TodosProvider>
</div>
)
const TodosList = () => {
const { todos } = useTodos();
return (
<>
{todos.map((todo, idx) => (
<SingleTodo />
))}
</>
)
}
And in another file
import { createContext, useContext, useState } from "react";
const TodosContext = createContext({});
export const TodosProvider = ({ children }) => {
const [todos, setTodos] = useState([{ text: 'a' }, { text: 'b' }, { text: 'c' }])
return (
<TodosContext.Provider value={{ todos }}>
{children}
</TodosContext.Provider>
)
}
export const useTodos = () => {
const todos = useContext(TodosContext)
return todos
}
How can I update a single todo inside the SingleTodo without:
1) Passing the map idx as a property to the SingleTodo and then from SingleTodo call a method of the TodosList provider passing the idx as a parameter
2) Giving an artificial id property to the todo. And then in TodosProvider update the todo that matches with that id.
The reasons for those restrictions are that:
1) Passing down the position of the todo in the rendering as a prop, invalidates the benefits of using context, which is to not have to do prop drilling
2) I don't think it's good to pollute the model with an artificial id just for state management.
I'd like to be able to create a SingleTodoContext and instantiate a SingleTodoProvider in each iteration of the loop
const TodosList = () => {
const { todos } = useTodos();
return (
<>
{todos.map((todo, idx) => (
<SingleTodoProvider key={idx} loadFrom={todo}>
<SingleTodo />
</SingleTodoProvider>
))}
</>
)
}
But that doesn't work because the provider would then need to store the loadFrom property as a state, and that would break the sync between the list todo, and the single todo.
So, how do I update a single item inside a list without prop drilling the position of the item in the list? I don't want to use Redux
You can pass methods for updating the values in context as part of your context. Here is an example based on your code (sort of all crammed together):
import React from "react";
import "./styles.css";
import { createContext, useContext, useState } from "react";
const TodosContext = createContext({});
export const TodosProvider = ({ children }) => {
const [todos, setTodos] = useState([
{ text: "a" },
{ text: "b" },
{ text: "c" }
]);
const selectTodo = (todo, idx) => {
console.log(
"do something with the todo here and then call setTodos, or something else?",
todo.text,
idx
);
// setTodos(prev => /* Do something here to update the list */)
};
return (
<TodosContext.Provider value={{ selectTodo, todos }}>
{children}
</TodosContext.Provider>
);
};
export const useTodos = () => {
const todos = useContext(TodosContext);
return todos;
};
const Home = () => (
<div className="container">
<TodosProvider>
<TodosList />
</TodosProvider>
</div>
);
const SingleTodo = ({ todo, onClick }) => (
<div>
{todo.text} <button onClick={() => onClick(todo)}>Click Me!</button>
</div>
);
const TodosList = () => {
const { selectTodo, todos } = useTodos();
return todos.map((todo, idx) => (
<SingleTodo onClick={todo => selectTodo(todo, idx)} todo={todo} key={idx} />
));
};
export default function App() {
return (
<div className="App">
<h1>Hello CodeSandbox</h1>
<h2>Start editing to see some magic happen!</h2>
<Home />
</div>
);
}
Hope that helps!

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