javascript - What does the "..." (triple dot) notation in arrays mean?

Question

(This question already has answers here): question from:https://stackoverflow.com/questions/36095630/what-does-the-triple-dot-notation-in-arrays-mean

Answer 1

The ...(spread operator) works by returning each value from index 0 to index length-1:

As example:

[...'18'] // returns ['1', '8']

which would be the same as:

['18'[0], '18'[1]]

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Now, to get an array from 1 to 18, you can do this:

[...Array(19).keys()].slice(1)

Or this with map:

[...Array(18)].map(_=>i++,i=1)

Hope it helps.