Well, with Firefox 31 using Array(length).fill(0) to construct the the array could be the best solution as it preallocates the array in one go.
On 18 July 2014 00:42, Nicholas Nethercote <[email protected]> wrote: > In this case, maybe not, but there are many similar cases where using > a typed array is less feasible. > > Nick > > On Thu, Jul 17, 2014 at 2:18 PM, Igor Bukanov <[email protected]> wrote: >> Any reasons to avoid Uint16Array ? >> >> On 17 July 2014 08:08, Nicholas Nethercote <[email protected]> wrote: >>> Hi, >>> >>> Here's some code from pdf.js: >>> >>> function stringToArray(str) { >>> var length = str.length; >>> var array = []; >>> for (var i = 0; i < length; ++i) { >>> array[i] = str.charCodeAt(i); >>> } >>> return array; >>> } >>> >>> This kind of code shows up in a number of places in pdf.js. Pretty >>> simple -- filling in an array one element at a time. >>> >>> Underneath the covers, this causes the array to repeatedly double in >>> size, which is annoying. And I thought I could avoid it because we >>> know how big the array will be in advance. So I changed the 3rd line >>> to this: >>> >>> var array = new Array(length); >>> >>> but I still get the same sort of doubling behaviour under the covers. >>> >>> So then I tried reverting that change and inserting this line just >>> before the loop: >>> >>> array[length - 1] = 0; >>> >>> And now it avoids the doubling allocations -- the array elements are >>> allocated once, at the right size. But it feels dirty, and I don't >>> know if would give the same behaviour in other JS engines. >>> >>> Is there a "right way" to do this? >>> >>> Nick >>> _______________________________________________ >>> dev-tech-js-engine-internals mailing list >>> [email protected] >>> https://lists.mozilla.org/listinfo/dev-tech-js-engine-internals _______________________________________________ dev-tech-js-engine-internals mailing list [email protected] https://lists.mozilla.org/listinfo/dev-tech-js-engine-internals
