I'm looking for an implementation of createEmpties(nValues) as below:
var result = createEmpties(4);
console.log(result)
[[], [], [], []]
I tried using map:
new Array(nValues).map(_ => []);
but got this output:
[ <4 empty items> ]
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3 Answers
You can do it using Array.from.
const result = Array.from({ length: 4 }, () => []);
console.log(result);7 Comments
mplungjan
Interesting difference>
const result = Array.from({ length: 4 }, () => []); result[2].push("hello"); console.log(result); const result1 = new Array(4).fill([]); result1[2].push("hello"); console.log(result1); 
ATD
Derek - I've just been reading using fill to create array, could your method be used to create the array in that question?
Derek Wang
Array.fill fills object reference not creating new instance.
Ivar
@ATD It could yes, as explained in this answer. (I've just voted to close the one you mentioned as a duplicate of it.)
Derek Wang
stackoverflow.com/a/64230402/8202850, this explains about
Array.fill. |
The new Array, will not fill. Try Array(nValues).fill(null).map(_ => []). This should give you what you are looking for.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/fill
3 Comments
ATD
you should see this: fill array Using fill can cause problems. The recommendation there seems to be to use map instead of fill.
mplungjan
@ATD - interesting result:
const result = Array.from({ length: 4 }, () => []); result[2].push("hello"); console.log(result); const result1 = new Array(4).fill([]); result1[2].push("hello"); console.log(result1); ATD
@mplungjan Yep - that was what led to create array using fill The link to mozilla above actually mentions that (though not entirely clearly) as the last point in the Description section.
Here's a function that gives you exactly what you asked for:
function createEmpties(n) {
return Array(n).fill(new Array());
}
var result = createEmpties(4);
console.log(result)
2 Comments
Scott Sauyet
Have you tried this? It won't do what's presumably expected.
Matt D
Please don't post only code as answer, but also provide an explanation what your code does and how it solves the problem of the question. Answers with an explanation are usually more helpful and of better quality, and are more likely to attract upvotes.