Below is my react functional component. Every 5 seconds I’m updating the time state and showing the time (via showTime()).
I also have a button that, when clicked, will push the current time to the timeList state (which is an array).
However so far I’m getting a bug in the handleClick function. What I want to happen is to push the current time onto the empty timeList array (timeList.push(time)). So timeList would be something like this: [’12:34:57′]. However instead timeList is 1 when the button is pushed.
import React, {useState, useEffect} from 'react';
function App() {
const [time, setTime] = useState(null);
const [timeList, setTimeList] = useState([]);
useEffect(
() => {
calcTime();
}, [time]
);
const calcTime = () => {
setTimeout(
() => {
const today = new Date();
const timeNow = today.getHours() + ':' + today.getMinutes() + ':' + today.getSeconds();
setTime(timeNow);
}, 5000
);
};
const showTime = () => {
if (time) {
return <p>{time}</p>
} else {
return <p>No time yet</p>
}
};
const handleClick = () => {
if (time) {
const newTimeList = timeList.push(time);
console.log(newTimeList); // first time the button is pushed "1" is logged here
setTimeList(newTimeList);
}
};
const showTimeList = () => {
if (timeList.length) {
const timesArr = timeList.map((item) => {
return <p>item</p>
});
return timesArr;
} else {
return <p>Time list will go here</p>
}
};
return (
<div className="App">
{showTime()}
{showTimeList()}
<button onClick={handleClick}>Add this time to the time list</button>
</div>
);
}
export default App;
>Solution :
push returns new length of array. What you want is to append time to timeList
const handleClick = () => {
if (time) {
const newTimeList = [...timeList, time];
setTimeList(newTimeList);
// or
setTimeList(oldTimeList => ([...oldTimeList, time]));
}
};