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174

What's the point of .slice(0) here?

rated 0 times [ 181] [ 7] / answers: 1 / hits: 48143 / 14 Years ago, thu, february 17, 2011, 12:00:00

I was studying the jQuery source when I found this (v1.5 line 2295):

namespace = new RegExp((^|\.) +

  jQuery.map( namespaces.slice(0).sort(), fcleanup ).join(\.(?:.*\.)?) + (\.|$));

My question is, why use slice(0) here?

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kylanalis

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answered 14 Years ago ronniem · Accepted Answer

sort() modifies the array it's called on - and it isn't very nice to go around mutating stuff that other code might rely on.

slice() always returns a new array - the array returned by slice(0) is identical to the input, which basically means it's a cheap way to duplicate an array.