Benchmarks

benches.md

Array fill

Should you 'pre-allocate' the array with new Array(n)? yes

https://jsbench.me/45l02v2h9e/1

Replace whitespace in string

Replace newlines with empty string, replaceAll slightly faster (though has less browser support)

https://jsbench.me/a2l02vz8l8/1

Frequency table

Count the number of instances of a thing in an array using a number of sample codes from long stack overflow thread

https://stackoverflow.com/questions/5667888/counting-the-occurrences-frequency-of-array-elements/59225909#comment125913203_59225909

https://jsbench.me/2wkzzagdu3/1

Ultimately some bit twiddling wins

Object.fromEntries([]) vs new Map([])

https://jsbench.me/z4l0h7kso6/1

new Map() about 1.5x faster than Object.fromEntries

Using UInt8Array instead of adding to string for large list of items

UInt8Array is faster https://jsbench.me/gll0k715zn/1

Sort strings

toLocaleString a bit slower than sort with no args https://jsbench.me/ool0mt6kwf/2

CIGAR strings

Not using a regex can be about 35% faster in Chrome, in firefox the regex is a bit faster

• https://jsbench.me/gpl0pyj08n/1 (10 cigar ops)
• https://jsbench.me/gpl0pyj08n/3 (100 cigar ops)
• https://jsbench.me/gpl0pyj08n/3 (1000 cigar ops)

Even if you save the regex result and re-run it multiple times, not using a regex is still a bit faster

• https://jsbench.me/gpl0pyj08n/4 (10 cigar ops)
• https://jsbench.me/gpl0pyj08n/5 (100 cigar ops)
• https://jsbench.me/gpl0pyj08n/6 (1000 cigar ops)

Fastest buffer filling

A task to fill up a 'buffer' with a bunch of stuff, where there might be an unknown number of things Test array, UInt8Array, string https://jsbench.me/gll0k715zn/1

Similar one but fills up a string, but with a constant number of things. The result is dependent on size. On small size strings, string append faster. On larger strings, textdecoder faster

• small (len 100) https://jsbench.me/7ql0r1tlx1/1 string append wins
• med (len 1000) https://jsbench.me/7ql0r1tlx1/2
• large (len 10000) https://jsbench.me/7ql0r1tlx1/3 textdecoder wins

Flatten array with .flat() vs .concat

Have to be careful with blowing the stack with concat but for a small number of items, [].concat(...items) can be faster than items.flat()

https://jsbench.me/1el0ugfw9g/1

Accessing values of map

for of loop can be faster

• https://jsbench.me/xnl0ws0kfm/1 (10 entries in map)
• https://jsbench.me/xnl0ws0kfm/2 (1000 entries in map)
• https://jsbench.me/xnl0ws0kfm/3 (1000 entries in map)

Accessing keys of map

seen here https://stackoverflow.com/questions/69145734/fastest-way-to-loop-through-map-keys

the forEach can be faster

• https://jsbench.me/vvktg4gyf2/1

Filling up nested object in a sparse array

Not really any significant differences here

https://jsbench.me/73l1p556jq/1

Drawing many rectangles on canvas

You can combine many rect drawing commands into a single one with Path2D, and it can be significantly faster than many individual fillRect calls https://jsfiddle.net/antonphp/1ghLn4a9/57/

Destructuring an array can be somewhat slow

https://jsbench.me/eolakmvsor/1

This was also noted by v8 team in relation to React hooks and actively optimized for performance, but destructuring array appears to still be a little bit of a bottleneck https://docs.google.com/document/d/1hWb-lQW4NSG9yRpyyiAA_9Ktytd5lypLnVLhPX9vamE/edit