We Keep Coding

How do I update the textarea using useState?

I have a textarea array with values that can be updated. The text values in the array are updated when text is entered into the textarea. The array can also be updated externally.
The problem is that Textarea doesn't want to update its values with setState() like regular text does.
export function GameActions({}) {
const [array, setArray] = useState<Type>([]);
const changeText = (id: number, text: any) => {
actions[id].text = text;
setActions(actions);
};
return {actions.map((action, index) => (<Textarea
defaultValue={action.text}
onChange={(e) =>
changeText(index, e.currentTarget.value)
}
/>))};
};

Provided actions is an array state property, it should be:
setActions((actions)=>{
return actions.map((act,i)=>{
if(i == id) {
act.text = text;
}
return act;
});
});
When a state property is updated using its previous value, the callback argument should be used.
Also, to update an element of a state array, map should be used, rather than the indexation operator [].
Please read this article, to learn how to update state arrays.

Remove rows from state array

I have created a dynamic form which can have rows added and removed and are stored in a state array.
I need to remove the index passed into the function from the array, without storing a null or empty value.
This is my current code for removing the rows however this simply removes the last row and not the one required at index
const removeRow = (index) => {
setLocationRows((current) =>
current.filter((employee, i) => {
return index !== i;
})
);
};
This code removes the required index however sets the value to null / empty which messes up when after removing and adding rows.
setLocationsObj((current) => {
const copy = { ...current };
delete copy[index];
return copy;
});

Joe.
Im supposing you have something like this:
const [locationRows, setLocationRows] = useState([]);
const removeRow = (index) => {
setLocationRows(locationRows.filter((e,i)=> i !== index))
};
If so, try the above code.
For the complete CRUD operation you can use the following:
const addRow = (newRow) => {
setLocationRows([... locationRows, newRow])
};
const updateRow = (rowData) => {
setLocationRows(locationRows.map(e => {
if(e.id === rowData.id) return rowData;
else return e;
});
};
I hope this can help you!

I recently had to do something very similar and used the array splice method, as it allows you to remove the element at a specific index.
const removeRow = (index) => {
setLocationRows((rows) =>
// create deep copy
const newRows = JSON.parse(JSON.stringfy(rows));
// remove 1 element at index
newRows.splice(index, 1);
return newRows;
);
};
If you are dealing with any sort of nested array it's important to create a deep copy of that array, as the const copy = [...rows] method only creates a shallow copy and can cause all sorts of bugs when trying to manipulate the data further.
Hope this helps!

Nested Object mutates in React

I am in almost desperate need of help. I am a mechanical engineer and I'm doing a type of calculator for my line of work. I have had an issue I've spent weeks on. I can't seem to solve it.
To not bore you with long code I will try to generalise it as much as possible.
I will first present an example code.
Then I will explain the expected behaviour and what is actually happening for me.
Finally I will explain what I have tried so far to solve this issue.
I will add more content at the bottom based on comments to help clarify my question.
CODE EXAMPLE
THE PARENT OBJECT
import {childObject} from "./childObject"
// in my code "childObject" are actually different from each other
const object1 = Object.assign({}, childObject);
const object2 = Object.assign({}, childObject);
const object3 = Object.assign({}, childObject);
const object4 = Object.assign({}, childObject);
const object5 = Object.assign({}, childObject);
const object6 = Object.assign({}, childObject);
const exampleObject = {
name: "foo",
otherInfo: "bar",
nestedObject:{
standardType: [object1, object2, object3],
specialType: [object4, object5, object6]
},
sumfunc(){}
}
THE CHILD OBJECT
export const childObject = {
name: "I'm losing my mind",
value: "" //<-- this will change
otherInfo: "please help me",
sumfunc(){}
}
EXPLAINING
What I am doing is the following:
Searchbar with all types of parentObjects.
Allowing user to select one or multiple of same or different parentObjects.
Storing the copied selection in a redux store.
Displaying the selection, each parentObject as a form. [see picture]
When typing in form the value of the nested object will change
Now... The issue is when I open the searchbar and select the same parentObject, thus copying it, all its values are mutated. As seen in picture above.
WHAT I HAVE TRIED
I have tried to use lodash clone and deepClone on the selected parentObject.
I have tried to use loads clone and deepClone on the selected childObjects.
I have tried, since the object have the same structure, to go through all key value pairs and shallow copy them.
I have tried to not send the parentObject via the searchbar component to the reducer, instead I just send a string and the reducer itself will add the parentObject to the store.
All methods that I've tried have not stopped the mutation. The deepClone method stopped the mutations, but in return the functions in the objects stopped working (maybe I need to bind it somehow?)
MORE CONTENT
The code that updates the value of the nestedObject
const inputsHandler = (e: React.ChangeEvent<HTMLInputElement>) => {
const formCopy = Object.assign({}, formEQ);
const inputFieldName = e.target.name;
// if anything other than a empty, number or decimal inputted, then return
const isNum = e.target.value.match(/^(?:\d{1,8}(?:\.\d{0,8})?)?$/);
if (!isNum) return;
// Update priority list to calculate the last updated input
formCopy.priorityList = formCopy.priorityList.sort((a, b) => {
if (a === inputFieldName) return 1;
if (b === inputFieldName) return -1;
else return 0;
});
// Update selected input field
formCopy.inputs[calcmode] = formCopy.inputs[calcmode].map((input) => {
if (input.name === inputFieldName) {
input.value = e.target.value;
}
return input;
});
// If more than two inputs empty do not calculate
const emptyInputs = formCopy.inputs[calcmode].reduce(
(acc, nV) => (nV.value === "" ? (acc += 1) : acc),
0
);
// Calculate the last edited input field
formCopy.inputs[calcmode] = formCopy.inputs[calcmode].map((input) => {
if (input.name === formCopy.priorityList[0] && emptyInputs <= 1) {
const calculatedValue = formCopy.calculate(
formCopy.priorityList[0],
calcmode
);
input.value = Number(calculatedValue).toFixed(2);
}
return input;
});
// Final set hook, now with calculated value
setformEQ({ ...formCopy });
};
Please good people of StackOverFlow... Help me!

Your code has few problems :
you are filtering based on name property of child object and all of them has the same name. Always provide unique id to the objects so that they can be differentiated in easy manner.
Your filter logic is so wrong :
formCopy.inputs[calcmode] = formCopy.inputs[calcmode].map((input) => {
if (input.name === inputFieldName) {
input.value = e.target.value; // < -- Culprit
}
return input;
});
Never mutate inline, always create a new copy.
This is how your code change function should be (I have removed dynamic key selection for clarity) :
const change = (e, id) => {
const inputFieldName = e.target.name;
// local copy of array
const nestedArr = [...qform.nestedObject.standardType];
// finding item to be updated
const index = nestedArr.findIndex((i) => i.id === id);
console.log({ index, inputFieldName, e, id });
if (index !== -1) {
const item = nestedArr[index];
item.value = e.target.value;
nestedArr[index] = item;
// deep copy till k depth where k is the key to be updated
const newObject = {
...qform,
nestedObject: {
...qform.nestedObject,
standardType: [...nestedArr],
},
};
setQform(newObject);
}}
Check this Example : Demo

How to change the property of an object inside an array propertly in react

this.state = {
myArray = [
{
name:"cat",
expand:false
}
]
}
clickItem(item){
item.expand = true;
this.setState({})
}
this.state.myArray.map((item) =>{
return <div onClick={()=>this.clickItem(item)}>{item.name}</div>
})
In React, i have a simple array of objects,
when i click on one of theses object, i want to change their prop and update the state, what is the proper way of doing this.
i feel like there could be a better way

You need to copy your state, update the copied state and the set the state.
this.state = {
myArray = [
{
name:"cat",
expand:false
}
]
}
clickItem(key){
let items = this.state.myArray;
items[key].expand = true;
this.setState({items})
}
this.state.myArray.map((key, item) =>{
return <div onClick={()=>this.clickItem(key)}>{item.name}</div>
})

Okay, a couple of things.
You're mutating the state directly which is going to fail silently and you're also missing the key prop on your <div.
This is easily resolved though by using the data you have available to you. I don't know whether each name is unique but you can use that as your key. This helps React decide which DOM elements to actually update when state changes.
To update your item in state, you need a way to find it within the state originally, so if name is unique, you can use Array.prototype.find to update it.
clickItem(item) {
const targetIndex = this.state.items.find(stateItem => stateItem.name === item.name)
if (targetIndex === -1)
// Handle not finding the element
const target = this.state.items[targetIndex]
target.expand = !target.expand // Toggle instead of setting so double clicking works as expected.
this.setState({
items: this.state.items.splice(targetIndex, 1, target) // This replaces 1 item in the target array with the new one.
})
}
This will update state and re-render your app. The code is untested but it should work.

Remove value from state (set new state)

I am trying to remove a value from my state.
I am using .filter as I believe this is the simplest way of doing it. I also want to implement an undo function ( but that's outside the scope of this question).
I have put this code in a sandbox
https://codesandbox.io/s/yrwo2PZ2R
class App extends React.Component {
constructor(props) {
super(props);
this.state = {
movies: x.movies,
};
}
remove = (e) => {
e.preventDefault();
console.log('remove movie.id:', e.target.value)
const index = e.target.value
this.setState({
movies: this.state.movies.filter((_, e) => e.id !== index)
});
}
render() {
return (
<div>
{this.state.movies.map(e =>
<div key={e.id}>
<li>{e.name} {e.id}</li>
<button value={e.id} onClick={this.remove}>remove</button>
</div>,
)}
</div>
);
}
}

Two problems.
First of all, the index you're getting from the event target value is a string, but you're comparing against a number. Change the index declaration as follows:
const index = Number(e.target.value);
Secondly, your filter is a little off. This will work:
this.state.movies.filter(movie => movie.id !== index)

The problem is index has string type, but id in objects has number type. You need type cast, for example:
const index = Number(e.target.value);
Other than that, you have some wrong _ in callback of filter function call. You don't need it. You need:
this.state.movies.filter(e => e.id !== index)
By the way I don't recommend to name values this way. Why e? You have array of movies. Use movie. Why index? You have id to remove. Then use idToRemove name.
You also have problem with adding items.
Firstly, you can add items like this:
this.setState({
movies: [...this.state.movies, { name: item.value.name, id: item.value.id }],
})
Another point: you have to autoincrement id. You can store last value in a variable. this.idCounter for example. And add will look like:
this.setState({
movies: [...this.state.movies, { name: item.value.name, id: this.idCounter++ }],
})
Example: https://codesandbox.io/s/2vMJQ3p5M

You can achieve the same in the following manner
remove = (e) => {
e.preventDefault();
console.log('remove movie.id:', e.target.value)
const index = e.target.value
var movies = [...this.state.movies]
var idx = movies.findIndex((obj) => obj.id === parseInt(index))
movies.splice(idx, 1);
this.setState({
movies
});
}
Also use parseInt to convert index to a string before comparing.
Directly setting the current state from the previous state values can cause problems as setState is asynchronous. You should ideally create a copy of the object and delete the object using splice method
CODESANDBOX