Develop Reference

Can't update state in React via key event

I'm making a calculator with React, when I click the divs they trigger a function to update the state which goes into the display output of the calculator, I have no problem at all doing this with clicking the divs. This is the code that is working as expected:
const Calculator = () => {
const initialState = {
val: "0",
}
const [value, setValue] = useState(initialState);
const sendCharacter = (number) =>{
let str = number.toString();
if (value.val != "0") {
const conc = value.val.concat(str);
setValue({
val: conc
});
} else {
setValue({
val: str
});
}
};
return (
<div id='calculator'>
<div id='display'>{value.val}</div>
<div id='one' className='numbers keys' onClick={() => sendCharacter(1)}>1</div>
</div>
);
Now, I want to do the same but instead of clicking div id="one" to add "ones" to my state I want those ones added to the state when I press the key 1. I added an eventsListener via useEffect() that loads only once after initial render. When I click 1 it calls the exact same function with the same exact argument that is called when clicking which is sendCharacter(1), here is my code:
useEffect(() => {
console.log("useEffect");
document.addEventListener("keyup", detectKey, true);
}, []);
const detectKey = (e) => {
if (e.key == "1") {
sendCharacter(1)
}
};
However when I press the i key I'm only able to update the state only the first time, if I try to add the second digit to my number it acts as if my actual state was "0" instead of "1" which doesn't allow it to enter the if statement.
To be clear and short: If if click my div id="one" I can enter the first condition of my if statement and update val via my conc variable, if i do it pressing the key i it always enters the else statement.
if (value.val != "0") {
const conc = value.val.concat(str);
setValue({
val: conc
});
} else {
setValue({
val: str
});
}
I tried logging messages everywhere and to see if my argument "1" is the same via clicking or via pressing my key, they send the exact same value, I'm totally lost in here and frustrated because I've got more than 1 hour trying to figure out what's going on. Also, I checked to see if the component was rendering before pressing the key, which was not the case.
BTW sorry for my English, not my first language, if someone can help me and needs clarification on one part I will answer asap, thanks in advance.

It seems you are falling into closures trap. Try updating your sendCharacter code to following.
const sendCharacter = (number) =>{
let str = number.toString();
setValue(value => {
if (value.val != "0") {
const conc = value.val.concat(str);
return {
val: conc
};
} else {
return {
val: str
};
}
});
};

React: Handling focus using array of useRef

I have created a basic Todo app but having a hard time in implementing proper focus into it. Following are the requirements for focus:
Focus should be on the newly created input field when "Add" is clicked so the user can begin typing right away.
On deleting an item "Button X", focus will move to the input field in the row which replaced the deleted row, nowhere if there are no fields left, or on the new last row if the last row was deleted.
On moving an item up, focus should be placed on the newly moved field, and all associated buttons should move alongside the element. If a field is already at the top of a list, no reordering should occur, but focus should be transferred to the topmost field nonetheless.
On moving an item down, same principle should apply here (focus should be placed on the field that is moved down). If its the last field, focus it nonetheless.
Here is my implementation.
App.js:
import React, { useState, useRef } from "https://cdn.skypack.dev/react#17.0.1";
import ReactDOM from "https://cdn.skypack.dev/react-dom#17.0.1";
const App = () => {
const [myRows, setMyRows] = useState([]);
const focusInput = useRef([]);
const onAddRow = () => {
setMyRows((prevRows) => {
return [
...prevRows,
{ id: prevRows.length, text: "", up: "↑", down: "↓", delete: "X" },
];
});
focusInput.current[myRows.length - 1].focus();
};
const onMoveUp = (index) => (event) => {
const currentState = [...myRows];
if (index !== 0) {
const prevObject = currentState[index - 1];
const nextObject = currentState[index];
currentState[index - 1] = nextObject;
currentState[index] = prevObject;
setMyRows(currentState);
}
};
const onMoveDown = (index) => (event) => {
const currentState = [...myRows];
if (index !== myRows.length - 1) {
const currObject = currentState[index];
const nextObject = currentState[index + 1];
currentState[index] = nextObject;
currentState[index + 1] = currObject;
setMyRows(currentState);
}
};
const onDelete = (index) => (event) => {
const currentState = [...myRows];
currentState.splice(index, 1);
setMyRows(currentState);
};
const onTextUpdate = (id) => (event) => {
setMyRows((prevState) => {
const data = [...prevState];
data[id] = {
...data[id],
text: event.target.value,
};
return data;
});
};
return (
<div className="container">
<button onClick={onAddRow}>Add</button>
<br />
{myRows?.map((row, index) => {
return (
<div key={row.id}>
<input
ref={(el) => (focusInput.current[index] = el)}
onChange={onTextUpdate(index)}
value={row.text}
type="text"></input>
<button onClick={onMoveUp(index)}>{row.up}</button>
<button onClick={onMoveDown(index)}>{row.down}</button>
<button onClick={onDelete(index)}>{row.delete}</button>
</div>
);
})}
</div>
);
}
ReactDOM.render(<App />,
document.getElementById("root"))
In my implementation when I click Add, focus changes but in unexpected way (First click doesn't do anything and subsequent click moves the focus but with the lag, i.e. focus should be on the next item, but it is at the prior item.
Would really appreciate if someone can assist me in this. Thanks!

The strange behaviour that you observe is caused by the fact that state updates are asynchronous. When you, in onAddRow, do this:
focusInput.current[myRows.length - 1].focus()
then myRows.length - 1 is still the last index of the previous set of rows, corresponding to the penultimate row of what you're actually seeing. This explains exactly the behaviour you're describing - the new focus is always "one behind" where it should be, if all you're doing is adding rows.
Given that description, you might think you could fix this by just replacing myRows.length - 1 with myRows.length in the above statement. But it isn't so simple. Doing this will work even less well, because at the point this code runs, right when the Add button is clicked, focusInput hasn't yet been adjusted to the new length, and nor in fact has the new row even been rendered in the DOM yet. That all happens a little bit later (although appears instantaneous to the human eye), after React has realised there has been a state change and done its thing.
Given that you are manipulating the focus in a number of different ways as described in your requirements, I believe the easiest way to fix this is to make the index you want to focus its own piece of state. That makes it quite easy to manage focus in any way you want, just by calling the appropriate state-updating function.
This is implemented in the code below, which I got working by testing it out on your Codepen link. I've tried to make it a snippet here on Stack Overflow, but for some reason couldn't get it to run without errors, despite including React and enabling Babel to transform the JSX - but if you paste the below into the JS of your Codepen, I think you'll find it working to your satisfaction. (Or, if I've misinterpreted some requirements, hopefully it gets you at least a lot closer than you were.)
Rather than just leaving you to study the code yourself though, I'll explain the key parts, which are:
the introduction of that new state variable I just mentioned, which I've called focusIndex
as mentioned, the calling of setFocusIndex with an appropriate value whenever rows are added, removed or moved. (I've been trying to follow your requirements here and it seems to work well to me, but as I said, I may have misunderstood.)
the key is the useEffect which runs whenever focusIndex updates, and does the actual focusing in the DOM. Without this, of course, the focus will never be updated on calling setFocusIndex, but with it, calling that function will "always" have the desired effect.
one last subtlety is that the "always" I put above is not strictly true. The useEffect only runs when focusIndex actually changes, but when moving rows there are some situations where it is set to the same value it had before, but where you still want to move focus. I found this happening when clicking outside the inputs, then moving the first field up or the last one down - nothing happened, when we want the first/last input to be focused. This was happening because focusIndex was being set to the value it already had, so the useEffect didn't run, but we still wanted it to in order to set the focus. The solution I came up with was to add an onBlur handler to each input to ensure that the focus index is set to some "impossible" value (I chose -1, but something like null or undefined would have worked fine as well) when focus is lost - this may seem artificial but actually better represents the fact that when the focus is on no inputs, you don't want to have a "sensible" focusIndex, otherwise the React state is saying one of the inputs is focused, when none are. Note that I also used -1 for the initial state, for much the same reason - if it starts at 0 then adding the first row doesn't cause focus to change.
I hope this helps and my explanations are clear enough - if you're confused by anything, or notice anything going wrong with this implementation (I confess I have not exactly tested it to destruction), please let me know!
import React, { useState, useRef, useEffect } from "https://cdn.skypack.dev/react#17.0.1";
import ReactDOM from "https://cdn.skypack.dev/react-dom#17.0.1";
const App = () => {
const [myRows, setMyRows] = useState([]);
const focusInput = useRef([]);
const [focusIndex, setFocusIndex] = useState(-1);
const onAddRow = () => {
setMyRows((prevRows) => {
return [
...prevRows,
{ id: prevRows.length, text: "", up: "↑", down: "↓", delete: "X" },
];
});
setFocusIndex(myRows.length);
};
useEffect(() => {
console.log(`focusing index ${focusIndex} in`, focusInput.current);
focusInput.current[focusIndex]?.focus();
}, [focusIndex]);
const onMoveUp = (index) => (event) => {
const currentState = [...myRows];
if (index !== 0) {
const prevObject = currentState[index - 1];
const nextObject = currentState[index];
currentState[index - 1] = nextObject;
currentState[index] = prevObject;
setMyRows(currentState);
setFocusIndex(index - 1);
} else {
setFocusIndex(0);
}
};
const onMoveDown = (index) => (event) => {
const currentState = [...myRows];
if (index !== myRows.length - 1) {
const currObject = currentState[index];
const nextObject = currentState[index + 1];
currentState[index] = nextObject;
currentState[index + 1] = currObject;
setMyRows(currentState);
setFocusIndex(index + 1);
} else {
setFocusIndex(myRows.length - 1);
}
};
const onDelete = (index) => (event) => {
const currentState = [...myRows];
currentState.splice(index, 1);
setMyRows(currentState);
const newFocusIndex = index < currentState.length
? index
: currentState.length - 1;
setFocusIndex(newFocusIndex);
};
const onTextUpdate = (id) => (event) => {
setMyRows((prevState) => {
const data = [...prevState];
data[id] = {
...data[id],
text: event.target.value,
};
return data;
});
};
return (
<div className="container">
<button onClick={onAddRow}>Add</button>
<br />
{myRows?.map((row, index) => {
return (
<div key={row.id}>
<input
ref={(el) => (focusInput.current[index] = el)}
onChange={onTextUpdate(index)}
onBlur={() => setFocusIndex(-1)}
value={row.text}
type="text"></input>
<button onClick={onMoveUp(index)}>{row.up}</button>
<button onClick={onMoveDown(index)}>{row.down}</button>
<button onClick={onDelete(index)}>{row.delete}</button>
</div>
);
})}
</div>
);
}
ReactDOM.render(<App />,
document.getElementById("root"))

trying to make a mark off for the to do App

I am currently busy trying to make a mark off to the list when it is done for the to-do app.
here is the JS code for it:
let tasks = [];
function todo(text) {
const todo = {
text,
checked: false,
id: Date.now(),
};
tasks.push(todo);
displaytasks(todo);
}
const list = document.querySelector('.list')
list.addEventListener('click', event =>{
if(event.target.classList.contains('js-tick')){
const itemKey = event.target.parentElement.dataset.key;
toggleDone(itemkey);
}
});
function toggleDone(key)
{
const index = tasks.findIndex(item => item.id === Number(key));
tasks[index].checked =!tasks[index].checked;
displaytasks(tasks[index]);
}
I have the tasks displaying, but it does not mark off when I click the circle that makes a tick and a line through.
In the console, I do not see it firing at all. As you can see I passed through the toggleDone(itemkey) to the function toggleDone(key)

changed
const itemKey = event.target.parentElement.dataset.key;
toggleDone(itemkey);
to
toggleDone(itemKey);
which fixed it.

Using onClick to remove item from one array and place in another in React

I want to be able to click on a certain element and then remove it from the player1 array and place it into the playCard array. Currently this is attached to a button on the page.
choseCard = () => {
this.setState(({
playCard,
player1
}) => {
return {
playCard: [...playCard, ...player1.slice(0, 1)],
player1: [...player1.slice(1, player1.length)]
};
});
}
Currently this takes the first item from the player1 array and places it in the playCard array. I want to be able to select a certain element(card) from the player array instead of just taking the first element. I'm having a hard time thinking of the way to do this in react as I am still a beginner.
Is there a way to maybe move the selected card to the first element then use the above code?

try passing the index of element you are clicking on to the function, this might possibly work...
choseCard = (index) => {
this.setState(({playCard, player1}) =>
{
return
{
playCard: [...playCard, ...player1.slice(index, 1)],
player1: [...player1.slice(0, index),...player1.slice(index,player1.length)]
};
});
}

You can insert whatever logic you need right above the return statement, then return the results:
choseCard = () => {
this.setState(({playCard, player1}) => {
// change `index` to whichever index you want to remove
const index = 1;
const toInsert = player1[index];
const player1Copy = player1.slice();
player1Copy.splice(index, 1);
const playCardCopy = playCard.slice();
playCardCopy.push(toInsert);
return {
playCard: playCardCopy,
player1: player1Copy,
};
});
}

you could pass the card object in the choseCard function
choseCard(card) => {
const {playCard, player1} = this.state;
return this.setState({
playCard: playCard.concat(card),
player1: player1.filter(c => c.id !== card.id)
});
}
this is also under the assumption that each card has a unique identifier.

React autocomplete in a textarea like in an IDE (e.g. VS Code, Atom)

I try to code an auto completion feature like in the gif in React.
So suggestions appear while writing text.
However all packages I could find so far work
a) only in the beginning of the input/textarea (e.g. react-autosuggest)
b) or need a trigger character (like # or #) to open (e.g. react-textarea-autocomplete)
Do I miss some React limitation? Any hints / packages?

We ended up using the fantastic editor Slate.js.
The Mentions example can easily be changed so that the suggestions are triggered by any character (not only '#'). There you go: perfect auto suggest.

I'm actually having the same problem in regards to needing a textarea implementation, but I can help with autocomplete triggering behavior.
We have an implementation of template variables that look like this {{person.name}} which get resolved into whatever the actual value is.
In regards to the autocompletion being triggered only on the first word, you can get around that with a couple modifications to the required functions.
For instance my required functions look like this. (not a completely working example, but all the important bits)
const templateVars = Object.values(TemplateVarMap);
const variables = templateVars.map((templateVar) => {
return {
name: templateVar,
};
});
//This func, onChange, and onSuggestionSelected/Highlight are the important
//parts. We essentially grab the full input string, then slice down to our
//autocomplete token and do the same for the search so it filters as you type
const getSuggestions = (value) => {
const sliceIndex = value
.trim()
.toLowerCase()
.lastIndexOf('{{'); //activate autocomplete token
const inputValue = value
.trim()
.toLowerCase()
.slice(sliceIndex + 2); //+2 to skip over the {{
const inputLength = inputValue.length;
//show every template variable option once '{{' is typed, then filter as
//they continue to type
return inputLength === 0
? variables
: variables.filter(
(variable) => variable.name.toLowerCase().slice(0, inputValue.length) === inputValue
);
};
const getSuggestionValue = (suggestion) => suggestion.name;
const renderSuggestion = (suggestion) => <div>{suggestion.name}</div>;
onSuggestionsFetchRequested = ({ value }) => {
this.setState({
suggestions: getSuggestions(value),
});
};
onSuggestionsClearRequested = () => {
this.setState({
suggestions: [],
});
};
onChange = (event, { newValue }) => {
//onChange fires on highlight / selection and tries to wipe
//the entire input to the suggested variable, so if our value
//is exactly a template variable, don't wipe it
if (templateVars.includes(newValue)) {
return;
}
this.setState({
value: newValue,
});
};
//These both need to do similar things because one is a click selection
//and the other is selection using the arrow keys + enter, we are essentially
//manually going through the input and only putting the variable into the
//string instead of replacing it outright.
onSuggestionHighlighted = ({ suggestion }) => {
if (!suggestion) {
return;
}
const { value } = this.state;
const sliceIndex = value.lastIndexOf('{{') + 2;
const currentVal = value.slice(0, sliceIndex);
const newValue = currentVal.concat(suggestion.name) + '}}';
this.setState({ value: newValue });
};
onSuggestionSelected = (event, { suggestionValue }) => {
const { value } = this.state;
const sliceIndex = value.lastIndexOf('{{') + 2;
const currentVal = value.slice(0, sliceIndex);
const newValue = currentVal.concat(suggestionValue) + '}}';
this.setState({ value: newValue });
};
const inputProps = {
value: this.state.value,
onChange: this.onChange,
};
render() {
return (
<Autosuggest
suggestions={this.state.suggestions}
onSuggestionSelected={this.onSubjectSuggestionSelected}
onSuggestionHighlighted={this.onSubjectSuggestionHighlighted}
onSuggestionsFetchRequested={this.onSuggestionsFetchRequested}
onSuggestionsClearRequested={this.onSuggestionsClearRequested}
getSuggestionValue={getSuggestionValue}
renderSuggestion={renderSuggestion}
inputProps={inputProps}
/>
)
}
This lets me type something like This is some text with a {{ and have autocomplete pop up, upon choosing a selection it should go to This is some text with a {{person.name}}.
The only problem here is that it requires the final two characters in the input to be {{ (or whatever your token is) for the autocomplete box to come up. I'm still playing with cursor movement and slicing the string around in different ways so if I edit a template thats not at the end the box still pops up.
Hopefully this helps.

You can try react-predictive-text