usestate array push
setTheArray([...theArray, newElement]);usestate array push
setTheArray([...theArray, newElement]);functional component how to add to existing array react
const {useState, useCallback} = React;
function Example() {
const [theArray, setTheArray] = useState([]);
const addEntryClick = () => {
setTheArray([...theArray, `Entry ${theArray.length}`]);
};
return [
<input type="button" onClick={addEntryClick} value="Add" />,
<div>{theArray.map(entry =>
<div>{entry}</div>
)}
</div>
];
}
ReactDOM.render(
<Example />,
document.getElementById("root")
);how to set value in array react hook usestate
const[array,setArray]= useState([
{id: 1, value: "a string", othervalue: ""},
{id: 2, value: "another string", othervalue: ""},
{id: 3, value: "a string", othervalue: ""},
])
const updateItem =(id, whichvalue, newvalue)=> {
var index = array.findIndex(x=> x.id === id);
let g = array[index]
g[whichvalue] = newvalue
if (index === -1){
// handle error
console.log('no match')
}
else
setArray([
...array.slice(0,index),
g,
...array.slice(index+1)
]
);
}
//how to use the function
onPress={()=>updateItem(2,'value','ewfwf')}
onPress={()=>updateItem(1,'othervalue','ewfwf')}
/*
the first input of the function is the id of the item
the second input of the function is the atrribute that you wish to change
the third input of the function is the new value for that attribute
It's a pleasure :0
~atlas
*/react setstate in hooks to array of objects value
// sample datas structure
/* const datas = [
{
id: 1,
name: 'john',
gender: 'm'
}
{
id: 2,
name: 'mary',
gender: 'f'
}
] */ // make sure to set the default value in the useState call (I already fixed it)
const [datas, setDatas] = useState([
{
id: 1,
name: 'john',
gender: 'm'
}
{
id: 2,
name: 'mary',
gender: 'f'
}
]);
const updateFieldChanged = index => e => {
console.log('index: ' + index);
console.log('property name: '+ e.target.name);
let newArr = [...datas]; // copying the old datas array
newArr[index] = e.target.value; // replace e.target.value with whatever you want to change it to
setDatas(newArr); // ??
}
return (
<React.Fragment>
{ datas.map( (data, index) => {
<li key={data.name}>
<input type="text" name="name" value={data.name} onChange={updateFieldChanged(index)} />
</li>
})
}
</React.Fragment>
)Copyright © 2021 Codeinu
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