entering values into an array in react from given 2d array - reactjs

Question

I want to enter the first value from every array inside a 2d array, I get the 2d array from the server and my intentions are to use it in one of the client pages (as chart data).
Here is the relevant code:
React.useEffect(() => {
fetch("http://localhost:3001/bitcoin")
.then((res) => res.json())
.then((data) => setData(data.message))
.then((dates) => {
//code right here
})
}, []);
Any idea how to implement it?

Answer 1

first method :
you can use for...of like this :
const Arr = [
[ 1,2,3,4],
['one', 'two' , 'three'],
['un' ,'deux', 'trois' ],
]
const ArrOfFirstValues = []
for(key of Arr){
ArrOfFirstValues.push(key[0])
}
console.log(ArrOfFirstValues)
the output is : [ 1, 'one', 'un' ]
Second method :
you can use .map to iterate it :
const Arr = [
[ 1,2,3,4],
['one', 'two' , 'three'],
['un' ,'deux', 'trois' ],
]
console.log(Arr )
const ArrOfFirstValues = Arr.map(arr => arr[0])
console.log(ArrOfFirstValues)
the output will be :
[ 1, 'one', 'un' ]

Answer 2

It's too easy :
const twoDArray = [
["a", "b", "c"],
["A", "B", "C"],
["aa", "bb", "cc"],
["AA", "BB", "CC"] ]
const firstElements = twoDArray.map(item => item[0]);
console.log(firstElements);
// answer: [ 'a', 'A', 'aa', 'AA' ]
Let me know if it is what you exactly need.
Update :
That was the main idea you need and you can implement like this:
React.useEffect(() => {
fetch("http://localhost:3001/bitcoin")
.then(res => res.json())
.then(jsonData => {
// I assume that jsonData is your 2D array
const twoDimensionArr = jsonData ;
setData(twoDimensionArr);
const firstElementsArr = twoDimensionArr.map(item => item[0]);
console.log(firstElementsArr);
})
}, []);