React Hooks append state
setTheArray(currentArray => [...currentArray, newElement])React Hooks append state
setTheArray(currentArray => [...currentArray, newElement])usestate array
setTheArray(oldArray => [...oldArray, 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
*/usestate nested object
const [currentApp, setCurrentApp] = useState({
userID: null,
hospitalName: null,
hospitalID: null,
date: null,
time: null,
timestamp: null,
slots: 1,
appointmentType: null
})
const [appointmentType, setAppointmentType] = useState({
Granulocytes: {
bloodType:null,
message: null
}
})
const handleGranChange = (e) => {
setAppointmentType({...appointmentType, Granulocytes : {
...appointmentType.Granulocytes,
[e.target.id] : e.target.value}
})
setCurrentApp({ ...currentApp, ['appointmentType'] : appointmentType })
console.log(currentApp)
}Copyright © 2021 Codeinu
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