I am trying to create an Array using new Array() and filling with index + 1 but somehow, though array is creating successfully but values are not filling correctly.
Code -
var aa = (new Array(4)).map((x, index) => {
return index + 1;
});
console.log(aa);Output - [undefined, undefined, undefined, undefined]
Expected - [1, 2, 3, 4]
Let me know what I am doing wrong here.
map only visits entries that actually exist, it skips gaps in sparse arrays.
There are various ways to do this:
You can use Array.from and its mapping callback:
const as = Array.from(Array(4), (_, index) => index + 1);
console.log(as);You can use a simple for loop:
const as = [];
for (let index = 1; index <= 4; ++index) {
as.push(index);
}
console.log(as);You can use fill and then map:
const as = Array(4).fill().map((_, index) => index + 1);
console.log(as);A variant of fill+map, you can use spread as Igor shows.
Array(size + 1).fill().unshift() or whatever other method you may prefer splice, slice, etc.undefined. The OP wants to fill it with the index + 1.[...Array(4)].map((v, i) => i + 1)
