How spread operator working here with Array keys

Question

Could someone explain how this [...Array(10).keys()]; working and logging 0 to 9 index?

console.log([...Array(10).keys()]);

Do you know what [`keys()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/keys) does? I am not sure what part you are not sure about. — epascarello, Aug 24 '22 at 17:47
So it takes the iterator and converts it into an array. Still not sure what you are looking for in an answer. — epascarello, Aug 24 '22 at 17:50
i want to know how that spread and key working together @Amaarockz — NewJS, Aug 24 '22 at 17:50
Keys returns an iterator that has the values of 0-9 and the spread takes the iterator and converts those values into an array. Quicker way of making an array for increasing numbers. https://stackoverflow.com/questions/3746725/how-to-create-an-array-containing-1-n — epascarello, Aug 24 '22 at 17:52
keys() basically return the indices of the Array(10) as an iterator, the square brackets then converts the iterator into 'list'. learn more [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/keys] — pyzer, Aug 24 '22 at 17:55

score 1 · Accepted Answer · answered Aug 24 '22 at 17:57

Here is the explanation

Case-1

const string = 'hello';

const array = [...string];

array;
// [ 'h' , 'e', 'l', 'l', 'o' ]

Case-2

Where we see spread operator acting as an eraser

[
  ...[1, 2, 3] // The dots erases the brackets
]

/*  Becoming this: */
[
  1, 2, 3 // "Erased"
]

Combining both of the above cases will help you on whats happening

1 Answers1