I'm trying set clickFavIconArray back to an empty array with the hook.
Basically, the setClickFavIconArray has a list of IDs the showFavIcon() checks that ID and if it contains the same ID I want to remove it from the array and update the setClickFavIconArray to the new Array.
However, it just seems to be adding on to the original clickFavIconArray no matter what. Is there a way to clear the clickFavIconArray state back to an [] empty array?
Some help here would be awesome.
const [clickFavIconArray, setClickFavIconArray] = useState([]);
function showFavIcon(id){
if (clickFavIconArray.includes(id)) {
const newArray = clickFavIconArray.filter(item => !id.includes(item))
setClickFavIconArray(newArray)
}
setClickFavIconArray([...clickFavIconArray, id])
}
Simply pass the new value of empty array to setClickFavIconArray():
setClickFavIconArray([])
To make sure that the id is not immediately added to the array again, add a return statement inside the if-statement.
const [clickFavIconArray, setClickFavIconArray] = useState([]);
function showFavIcon(id){
if (clickFavIconArray.includes(id)) {
const newArray = clickFavIconArray.filter(item => !id.includes(item));
setClickFavIconArray(newArray);
return; // make sure that the next line is not executed
}
setClickFavIconArray([...clickFavIconArray, id])
}
There are two issues with the code
filter function seems to be invalid it should be replaced with
clickFavIconArray.filter(item => id != item)
You are adding id again to the array with this
setClickFavIconArray([...clickFavIconArray, id])
If you want to remove id, there is no need for this line in your code.
However you can always set clickFavIconArray to an empty array state using this code:
setClickFavIconArray([])
Related
trying to push data coming to "id" to "selectedUserId" array, but first element is not inserting.
selectedUserId array does not contain first pushed element, push is only working from second element onwards.
const handleSelectOne=(e)=>{
const id = e.target.value;
console.log(id,"handling")
if(!selectedUserIds.includes(id))
{
selectedUserIds.push(id)
}
else
{
selectedUserIds.pop(id)
}
setCheckedStatusOne(!checkedStatusOne[id])
}
const handleDeleteSelectedClick=() =>{
let deletionItemsNo = selectedUserIds.length
selectedUserIds.map((id)=>{
return console.log(id, "<== element inside selecteduserids array")
})
console.log(deletionItemsNo, "<== number of elements in array")
}
output
console output
.pop() method doesn't accept any arguments. It used for removing the last array item.
To be able to insert element in the beginning you should use .unshift(id)
When you push an array, data is pushed. However if you check in console.log, data is not imported. It seems to be a delay. Can you tell me why is this happening?
is there solution for this?
Expected console.log result showing input, however empty array shows and if you click checkbox again then input appears.
const [checked, setChecked] = useState<number[]>([])
const handleAddListToArray = (id: number) => {
console.log(checked)
if (setChecked.includes(id)) {
setChecked(checked.filter((item) => item !== id))
} else {
setChecked([...checked, id])
}
}
--- checkbox compornent ---
const [isChecked, setIsChecked] = useState(false)
const handleChange = () => {
setIsChecked(!isChecked)
handleAddListToArray(id)
}
<Checkbox checked={isChecked} onClick={() => handleChange()} />
when you push an array, data is pushed however if you check in
console.log data is not inported. it seems to be a delay can you tell
me why is this happening?
The state-setting functions are asynchronous. In other words, if you wrote:
const [foo, setFoo] = useState(0);
setFoo(1);
console.log(foo); // logs 0, NOT 1
you would see 0 logged, not 1 ... at least initially. However, there'd be a log entry below that would show 1.
This is because set* function don't change the value in the function, but they do cause the component to be re-rendered after, which means the function is run again, and now uses the correct value..
however empty array shows and if you click checkbox again then input
appears.
It's because of this code:
setIsChecked(!isChecked)
Initially you set isChecked to an array:
setChecked(checked.filter((item) => item !== id))
But then you changed it to !isChecked ... a boolean. Once you change it to a boolean, you can't change it back to an array.
You check the setState-function if it includes the input, on your fourth row of code:
if (setChecked.includes(id))
I believe you want to chech the checked-state instead, like so:
if (checked.includes(id))
Also, consider using the useState-callback when you mutate your state based on the previous one. So instead of:
setChecked(checked.filter((item) => item !== id))
try:
setChecked((prevState) => prevState.filter((item) => item !== id))
You can also use this when you setting your isChecked state. This ensure that you get your latest known state and avoids getting in some wierd states because React updates the state asynchronous.
Some suggestions
if (setChecked.includes(id)) {
should be (setChecked is a function)
if (checked.includes(id)) {
For setChecked(checked.filter((item) => item !== id))
better usage will be
setChecked(prevCheckedValues => prevCheckedValues.filter((item) => item !== id));
This way you will always get the current checked values when you do a setChecked.
Another way to use this is via a useCallback and pass the dependency array as [checked]
If you want to print checked values each time its changed you can use a useEffect (docs) with correct dependency array.
Usage example
useEffect(()=>{
console.log("Checked", checked);
}, [checked])
I have an object that looks like this
const array_eps = {
episode3: ["https:\/\/www.youtube.com\/embed\/kzZ6KXDM1RI","https:\/\/www.youtube.com\/embed\/T8y_RsF4TSw","https:\/\/www.youtube.com\/embed\/qrtKLNTB71c","https:\/\/www.youtube.com\/embed\/qrtKLNTB71c","https:\/\/www.youtube.com\/embed\/qrtKLNTB71c","https:\/\/www.youtube.com\/embed\/qrtKLNTB71c"],
episode2: ["https:\/\/www.youtube.com\/embed\/qrtKLNTB71c"],
episode1: ["https:\/\/www.youtube.com\/embed\/qrtKLNTB71c"],
};
What i want to do here is get the first element of array that act as value in a object.
I'm already do something like this
array_eps[Object.keys(array_eps)[0]]
But it's return the whole array not only the first element.
Thankyou
const array_eps = {
episode3: ["https:\/\/www.youtube.com\/embed\/kzZ6KXDM1RI","https:\/\/www.youtube.com\/embed\/T8y_RsF4TSw","https:\/\/www.youtube.com\/embed\/qrtKLNTB71c","https:\/\/www.youtube.com\/embed\/qrtKLNTB71c","https:\/\/www.youtube.com\/embed\/qrtKLNTB71c","https:\/\/www.youtube.com\/embed\/qrtKLNTB71c"],
episode2: ["https:\/\/www.youtube.com\/embed\/qrtKLNTB71c"],
episode1: ["https:\/\/www.youtube.com\/embed\/qrtKLNTB71c"],
};
console.log(array_eps[Object.keys(array_eps)[0]][0]);
How would I go about deleting just a single item?
Provided I know the 'name' value ("To add") but I don't know the item ID value (-M0qUq...).
The following code works to delete the item, but I want to make it dynamic and not have to hardcode in the ID value.
handleRemove = (item) => {
db.ref('/items/-M0qUPNnHRbZAb1R3690/').remove();
}
Try the following:
let query = db.ref('items').orderByChild("name").equalTo("To add");
db.once('value').then((snapshot) => {
snapshot.forEach((subSnapshot) => {
let key = subSnapshot.key;
db.ref('items').child(key).remove();
});
});
First add a query equalTo, then iterate inside the returned result to be able to retrieve the key and then use remove() to delete.
I have a simple app which allows someone to add a numbers into an input, and have those numbers render onto the page (as inputs) which can be edited.
addSiblingValue(evt) {
this.setState({
currentObject: {
...this.state.currentObject,
numberOfSiblings: evt.target.value
}
});
add() {
const array = [...this.state.array, this.state.currentObject];
this.setState({
array
});
}
siblingCountChange(rowIndex, event) {
const array = [...this.state.array];
array[rowIndex].numberOfSiblings = event.target.value;
this.setState({ array });
}
So when I add a number it renders a new input with the value set to the number I've just added, but when I go to change that value, it now is affecting the first input.
The first row of inputs are using their own object currentObject which pushes to to the this.state.array, so I'm not sure why editing anything in that array would affect the currentObject?
Expected behaviour:
User enters a number into the input and clicks add
That input is rendered and can be edited independently
How do I achieve this or what is it I'm doing wrong here?
CodeSandbox
Thank you
When you add this.state.currentObject to the array, it works as an reference, so that the added object in the array and this.state.currentObject are the same object. You can prevent that by adding not the object itself, but a copy of the object into the array:
add() {
const array = [...this.state.array, {"numberOfSiblings": this.state.currentObject.numberOfSiblings}];
this.setState({
array
});
}
siblingCountChange(rowIndex, event) {
const array = [...this.state.array];
array[rowIndex].numberOfSiblings += parseInt(event.target.value);
this.setState({ array });
}
You were not adding the actual number to the current state. I also removed the value from the add like so:
<input
type="text"
onChange={this.siblingCountChange.bind(this, rowIndex)}
/>
You will need to put error handling on the state as a string plus a number leads to NaN error. As you can see the number is parsed before addition.
Thanks to dieckie for pointing me in the right direction. Unfortunately that particular solution did not work, but using Object.assign to create a reference and pushing that to the array did?
Posting here so it helps others/myself in future:
add() {
let copyOfCurrentObject = Object.assign({}, this.state.currentObject);
const array = [...this.state.array, copyOfCurrentObject];
this.setState({
array
})
}
This question was also helpful.