SyntaxFix

[javascript] Maximum size of an Array in Javascript

Like @maerics said, your target machine and browser will determine performance.

But for some real world numbers, on my 2017 enterprise Chromebook, running the operation:

console.time();
Array(x).fill(0).filter(x => x < 6).length
console.timeEnd();
  • x=5e4 takes 16ms, good enough for 60fps
  • x=4e6 takes 250ms, which is noticeable but not a big deal
  • x=3e7 takes 1300ms, which is pretty bad
  • x=4e7 takes 11000ms and allocates an extra 2.5GB of memory

So around 30 million elements is a hard upper limit, because the javascript VM falls off a cliff at 40 million elements and will probably crash the process.

EDIT: In the code above, I'm actually filling the array with elements and looping over them, simulating the minimum of what an app might want to do with an array. If you just run Array(2**32-1) you're creating a sparse array that's closer to an empty JavaScript object with a length, like {length: 4294967295}. If you actually tried to use all those 4 billion elements, you'll definitely your user's javascript process.

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