How to select data that satisfies a condition from multiple data.
I'm not good at using maps and filters. How to select data that satisfies a condition from multiple data.
sampleData
[
{
"dataList": [
{
"date": "2022-09-01T15:00:00Z",
"friendsIds": []
},
{
"date": "2022-09-02T15:00:00Z",
"friendsIds": []
},
{
"date": "2022-09-03T15:00:00Z",
"friendsIds": []
},
{
"date": "2022-09-04T15:00:00Z",
"friendsIds": [
6
]
},
{
"date": "2022-09-05T15:00:00Z",
"friendsIds": [
7,8,10
]
},
{
"date": "2022-09-06T15:00:00Z",
"friendsIds": [
8
]
},
{
"date": "2022-09-09T15:00:00Z",
"friendsIds": [
9
]
},
]
}
]
I want to get the first time when frends is not empty. However, the last time is obtained. And there is a type error.
const sample = React.useMemo(() => {
let arr[]:string[];
sampleData[0].dataList.map((list) => {
if(list.friends.length > 0) {
result = list.date;
return result;
}
});
return result;
}, [sampleData]);
console.log(sample);
result
2022-09-09T15:00:00Z
expectation
2022-09-04T15:00:00Z
Use array.find for this:
const sample = React.useMemo(() => {
return sampleData[0].dataList.find(x => x.friends.length)?.date
}, [sampleData]);