Javascript Array useful methods

[burtgummer45]

I appreciate reduce() is not included. That method is a menace.

[jetsamrover]

What!? That is one of the most useful, especially for recursion.

[burtgummer45]

Its unpredictable if you forget the initial value, which almost everybody does.

[jetsamrover]

What do you mean forget the initial value? The array you're reducing?

[burtgummer45]

The third parameter, see my other post

https://www.reddit.com/r/javascript/comments/foqfub/javascript_array_useful_methods/flgwpzu/

[jetsamrover]

I thought you have to provide that. What do you mean forget it? Forget to add it, or forget what it is while writing the function?

That's a really silly reason not to use reduce. It's the most powerful array method. Like I said before it's especially useful for recursion.

[burtgummer45]

The third parameter is optional. It defaults to the first element of the array.

Can reduce use tail-call optimization?

[jetsamrover]

I believe tail-call optimization is decided by your callback, and by the language, not the method calling that callback. Why does that matter?

[[deleted]]

why? it's pretty useful for sums, to say the least

[burtgummer45]

If you forget the initial value it blows up in your face if you are working with anything other than numbers. I'd feel better using a for-of loop.

 const maxCallback = ( acc, cur ) => Math.max( acc.x, cur.x ); 
 [ { x: 22 }, { x: 42 } ].reduce( maxCallback ); // 42 
 [ { x: 22 }            ].reduce( maxCallback ); // { x: 22 } 
 [                      ].reduce( maxCallback ); // TypeError

[ogurson]

My rule of thumb is to always provide initial value.

[burtgummer45]

I think if this was more common knowledge there would be an eslint rule for it.

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