Hi i am new ish to JavaScript/React and I am currently making a project to practice it more.
I have an expenses list with some expenses all with a unique Id stored as props.items but i'm trying to add a delete button so that an expense will be removed from props.items when its clicked. Is there a way i can remove an item from props.items with the use of the unique ID?
Currently I have this where idNumber is the unique id sent back from the child component ExpenseItem
const onRemoveExpense = (idNumber) => {
console.log("remove clicked", idNumber)
console.log(props.items, "<- all items")
}
return (
<ul className='expenses-list'>
{props.items.map((expense) => (
<ExpenseItem
key={expense.id}
value={expense.id}
title={expense.title}
amount={expense.amount}
date={expense.date}
removeExpense={onRemoveExpense}
/>
))}
</ul>
);
}
Thanks for the help!
The biggest hurdle I see here is that your items array is not in the state of the component in question-- it is passed in as props. So you'd want to define your deletion script in which component is holding the items in its component state. You'd write it somewhere along the lines of:
const onRemoveExpense = (idNumber) => {
this.setState((state, props) => {
// get items from current state
const { items } = state;
// get a new array with only those items that do *not* have the id number passed
const newItems = items.filter((item) => item.id !== idNumber);
// return it to set the new state
return newItems;
});
}
This would obviously need to be adjusted to your specific state and component structure. You'd then pass this as a prop along with the items to the component in question, and call it to trigger a deletion.
For a "hide" function instead of a delete one, you could try adding a shown boolean prop and then change that on click.
But to actually delete it, you'll need to have your items stored in state.
You could try something like this:
const [items, setItems] = useState(props.items)
// set the initial state as `props.items`
// (I'm assuming the code snippet you shared exists inside a functional component)
const onRemoveExpense = (idNumber) => {
console.log("remove clicked", idNumber)
console.log(props.items, "<- all items")
const newItems = items.filter(({ id }) => id !== idToDelete)
setItems(newItems)
}
return (
<ul className='expenses-list'>
{items.map((expense) => (
<ExpenseItem
key={expense.id}
value={expense.id}
title={expense.title}
amount={expense.amount}
date={expense.date}
removeExpense={() => onRemoveExpense(expense.id)}
/>
))}
</ul>
);
}
I might be forgetting something though—I haven't tested the above code. You might need to have a useEffect() to make it re-render properly when the state changes.
Or you can manage the state in the component that is defining items for this component.
Related
I have a list of items and I want to bring some data from a child component to the "source of truth", which items have been selected in this case, but the only way I can think of of specifying which list item has been selected is but using the event.target.id property. of which I specify in one of the child components. see below
constructor(props){
super(props)
this.state = {
showDialog : false,
preparedSpells: [],
}
}
onPrep(e){
let prepedSpells = this.state.preparedSpells
let targetSpell = Number(e.target.id)
if (prepedSpells.includes(targetSpell)){
let index = prepedSpells.indexOf(targetSpell)
prepedSpells.splice(index,1)
} else {
prepedSpells.push(targetSpell)
}
this.setState({
prepedSpells : prepedSpells
})
render(){
return(
<SpellList spells = {this.spells} onSpellClick = {this.onSpellClick} onClick = {this.onPrep}></SpellList>
);
I need the data to be at this level but I feel that there should be a way of setting the state in one of the list item components and then iterating through them all to find which are selected.
I know data only flows down in react but is there something im missing? or should I bottle up this feeling of wrongness
Looks like you're pretty close to correctness to me.
Let me tell you what I would change:
Instead of sending passing the whole event to "onPrep", you can just pass the id.
onPrep(targetSpell){
let prepedSpells = this.state.preparedSpells
if (prepedSpells.includes(targetSpell)){
let index = prepedSpells.indexOf(targetSpell)
prepedSpells.splice(index,1)
} else {
prepedSpells.push(targetSpell)
}
this.setState({
prepedSpells : prepedSpells
})
And I don't actually have the code for the SpellList component, but you should have something like this:
return (
<div>
{this.props.spells.map((spell) => {
return <button onClick={() => {this.props.onClick(spell.id)}}>{spell.name}</button>;
})}
</div>
);
That way you can pass whatever you want to the click event handler, and it makes things look cleaner.
I have a dropdown list that contains some cart items from a shop. I want the dropdown to re-render every time a cart item is added, but it doesn't and only shows my new cart addition when I close and open the cart again (remounts).
const CartDropdown = () => {
const {setCartProducts, cartProducts} = useContext(CartContext)
const {setProducts, currentProducts} = useContext(ProductsContext)
// useEffect(() => {}, [cartProducts])
const cleanCart = () => {
const cleanProducts = currentProducts
console.log(cleanProducts)
for (let i in cleanProducts) {
if (cleanProducts[i].hasOwnProperty('quantity')){
cleanProducts[i].quantity = 0
}
}
setProducts(cleanProducts)
setCartProducts([])
}
return(
<div className='cart-dropdown-container'>
<div className='cart-items' forceRemount={force}>
{cartProducts.map((product) => (
<div>
<img src={product.imageUrl}></img>
</div>)
)}
</div>
<button onClick={cleanCart}>LIMPAR</button>
<Button children={'FINALIZE PURCHASE'}/>
</div>
)
}
I want the CartDropdown to remount when the cartProducts changes.
It really depends on what those setters and getters on your useContext are returning.
Assuming they are from a useState(), then you have to make sure you always pass a different object to the setters.
From the docs:
Bailing out of a state update
If you update a State Hook to the same value as the current state,
React will bail out without rendering the children or firing effects.
(React uses the Object.is comparison algorithm.)
In other words, simply mutating currentProducts and calling setProducts passing the same (but now mutated) object will not trigger a reprender.
So your code
const cleanProducts = currentProducts
console.log(cleanProducts)
// Mutating cleanProducts
setProducts(cleanProducts)
Should be something like
const cleanProducts = [...currentProducts] // <--- changed this line
console.log(cleanProducts)
// Mutating cleanProducts
setProducts(cleanProducts)
And you have to do this everywhere you call setters.
Another thing, you should add a key attribute to elements used in a .map(). For instance:
{cartProducts.map((product) => (
<div key={product.imageUrl}>
<img src={product.imageUrl}></img>
</div>)
)}
I am using an array of components that are interested depending on various conditions i.e the order and number of elements in the array are dynamic as shown below:
useEffect(() => {
const comp = [];
// if(condition1===true){
comp.push(<MyComp onChange={onValueChange} />);
// }
// if(condition2===true){
comp.push(<YourComp onChange={onValueChange} />);
// }
// if(condition3===true){
comp.push(<HisComp onChange={onValueChange} />);
// }
setComponents(comp);
}, []);
To each of the components in the array, there could be some sort of input control like input-text, input-number, text-area, chips, radio, checkbox, etc.
So there is an onChange event linked to each of these components.
I am using a common onValueChange function which is passed as a callback to these components. In the onValueChange I need 2 things:
changed value (from child component)
activeIndex (from same component)
const onValueChange = (val) => {
console.log("onChange Valled", val, "activeIndex==", activeIndex);
};
But here I am not able to fetch the updated value on activeIndex, it always gives zero no matter in what active step I am in.
Sandbox DEMO
useEffect(() => {
setComponents((previousValues)=>{
// if you want to add on previous state
const comp = [...previousValues];
// if you want to overwrite previous state
const comp = [];
if(condition1===true){
comp.push();
}
if(condition2===true){
comp.push();
}
if(condition3===true){
comp.push();
}
return comp;
});
}, []);
Try using useCallback with dependency array. Also try to avoid storing components in state - the office advice - what shouldn’t go in state?
const onValueChange = useCallback((val) => {
console.log("onChange Valled", val, "activeIndex==", activeIndex);
},[activeIndex];
For rendering try something like below.
condition1===true && <MyComp onChange={onValueChange} />
or create a function which returns the component eg: getComponent(condition) and use this in render/return. Make sure you wrap getComponent in useCallback with empty dependency array []
I am trying to update state on click event using react hooks. State changes, but component doesn't rerender. Here is my code snippet:
function ThirdPage() {
const [selectedIngredients, setSelectedIngredients] = useState([])
const DeleteIngredient = (ingredient) => {
let selectedIngredientsContainer = selectedIngredients;
selectedIngredientsContainer.splice(selectedIngredientsContainer.indexOf(ingredient), 1);
setSelectedIngredients(selectedIngredientsContainer);
console.log(selectedIngredients);
}
const selectedIngredientsDiv = selectedIngredients.map(ingredient =>
(
<div className={styles.selectedIngredientsDiv}>{ingredient}
<div className={styles.DeleteIngredient}
onClick={() => {
DeleteIngredient(ingredient)}}>x</div></div>
))
return (
...
What am I doing wrong? Thanks in advance!
Issue with you splice as its not being saved to selectedIngredientsContainer. I would do following:
selectedIngredientsContainer = selectedIngredientsContainer.filter(value => value !== ingredient);
or
selectedIngredientsContainer.splice(selectedIngredientsContainer.indexOf(ingredient), 1 );
setSelectedIngredients([...selectedIngredientsContainer]);
Hope it helps.
normally I would leave an explanation on what's going on but tldr is that you should check first to make sure that you're array isn't empty, then you you can filter out the currentIngredients. Also you don't need curly brackets to call that function in the jsx but that can be personal flavor for personal code. I apologize if this doesn't help but I have to head out to work. Good luck!
function ThirdPage() {
const [selectedIngredients, setSelectedIngredients] = useState([]);
const DeleteIngredient = ingredient => {
// let selectedIngredientsContainer = selectedIngredients;
// selectedIngredientsContainer.splice(selectedIngredientsContainer.indexOf(ingredient), 1);
// setSelectedIngredients(selectedIngredientsContainer);
// console.log(selectedIngredients);
if (selectedIngredients.length > 0) {
// this assumes that there is an id property but you could compare whatever you want in the Array.filter() methods
const filteredIngredients = setSelectedIngredients.filter(selectedIngredient => selectedIngredient.id !== ingredient.id);
setSelectedIngredients(filteredIngredients);
}
// nothing in ingredients - default logic so whatever you want
// log something for your sanity so you know the array is empty
return;
};
const selectedIngredientsDiv = selectedIngredients.map(ingredient => (
<div className={styles.selectedIngredientsDiv}>
{ingredient}
<div className={styles.DeleteIngredient} onClick={() => DeleteIngredient(ingredient)}>
x
</div>
</div>
));
}
The answer is very Simple, your state array selectedIngredients is initialized with an empty array, so when you call map on the empty array, it will not even run once and thus DeleteIngredient is never called and your state does not change, thus no re-render happens
I have code where if a function is invoked it will call toggleCheckedUser and pass along information about which object property to toggle. Then saves the modified object back to state (selectedSendTo).
However, when I run this, the toggle it works, but when I try to edit a second property, before changing it I try console.log(selectedSendTo) I always get the initial value whether it be an empty object {} or false instead of the previously updated object.
When I use useEffect to spy on selectedSendTo I can see that the setSelectedSendTo() function correctly updated the object. So for some reason when I revisit the object it's empty.
const [selectedSendTo, setSelectedSendTo] = useState(false);
const toggleCheckedUser = (companyID, contactID) => {
console.log(companyID, contactID);
console.log(selectedSendTo); // THIS VALUE IS always the same as INITIAL value
console.log(selectedSendTo[companyID]);
if(selectedSendTo[companyID] &&
selectedSendTo[companyID][contactID] === true){
//remove it
delete(selectedSendTo[companyID][contactID]);
}else{
setSelectedSendTo({
...selectedSendTo,
[companyID]:{
...selectedSendTo[companyID],
[contactID]: true,
}
})
}
}
Here is the DOM:
<CustomCheckbox
className="person__checkbox" name={`checkbox-${contactID}`}
alreadySelected={
selectedSendTo[company.companyID] &&
selectedSendTo[company.companyID][contactID]
}
onChange={() => toggleCheckedUser(company.companyID, contactID)}
/>
UPDATE, A POSSIBLE SOLUTION
I found that the following works:
To be able to access the current value from useState I used useRef
const selectedSendToRef = useRef();
useEffect( () => {
selectedSendToRef.current = selectedSendTo;
}, [selectedSendTo])
Then inside of my function, I can use selectedSendToRef.current to access the most recent value of `selectedSendTo.
When updating state, I can access the most recent version from state using
setSelectedSendTo( prevValue => ....)
const toggleCheckedUser = (companyID, contactID) => {
console.log(companyID, contactID, selectedSendToRef.current);
console.log('selectedSendTo[companyID]: ', selectedSendTo[companyID]);
let newValue;
if(selectedSendToRef.current[companyID] &&
selectedSendToRef.current[companyID][contactID] === true){
newValue = false;
}else{
newValue = true;
}
setSelectedSendTo(prevValue => (
{
...prevValue,
[companyID]:{
...prevValue[companyID],
[contactID]: newValue,
}
}
));
}
UPDATE 2: The Real Solution
Okay so it seems like the problem was that even after a render, the child component was not receiving the updated state because of how I had used nested functions to create the elements.
Here is how I had things
<Main Component>
<div>
{Object_1}
<div>
</Main Componenent
and object_1 was defined something like this:
const Object_1 =
<React.Fragment>
<h1>Random Header</h1>
{StateObject_Containg_Elements}
</React.Fragment>
Now to create the state object that conatined the elements I wanted to display I was using a funciton called by a useEffect hook. Basically when the server sent back data that I needed, I would tell the useEffect hook to run a function called createElements
const createElements = (data) => {
const elements = Object.keys(data).map( item => return(
<ul>
{subFunction1(item)}
</ul>
subFunction1(item){
item.contacts.map( name => {
reutrn <CustomCheckbox name={name} checked={selectedSendTo[name]}
})
}
saveElementsToState(elements);
}
As you can see we basically have a function that runs 1 time (on server response) that triggers a function that creates the array of elements that we want to display which has its own nested subfunction that includes the child component that we are asking to watch a different state object to know whether it should be checked or not.
So What I did was simplify things, I turned {Object_1} into it's own functional component, lets call it <Object1 />. Inside the component instead of calling a function I just put the function code in there to loop through and return the elements (no longer saving elements to state) and lastly I no longer needed the useEffect since just updating the state object with the data once it gets it from the server would cause my subcomponent to re-render and create the elements. Inside the sub-component I simply return null if the data in state is null.
That fixed all my problems.
so now it looks something like this:
const Object1 = () => {
if(!data)return null;
return(
Object.keys(data).map( item => return(
<ul>
{subFunction1(item)}
</ul>
subFunction1(item){
item.contacts.map( name => {
reutrn <CustomCheckbox name={name} checked={selectedSendTo[name]}
})
}
)
}
return(
<div>
<Object1 /> //This is what contains/creates the elements now
</div>
)