Nit: you should use `.spilt(/\n/g)` to get all parts. I like the benchmarks here. That's much appreciated, and after further investigation, I found a *giant* WTF: https://jsperf.com/regexp-counting-2/8
TL;DR: for string character counting, prefer `indexOf`. For similar reasons to that JSPerf thing, I'd like it to be on the String prototype rather than the RegExp prototype, as in `str.count(/\n/)`. ----- Isiah Meadows [email protected] www.isiahmeadows.com On Sun, Jan 20, 2019 at 12:33 AM kai zhu <[email protected]> wrote: > > benchmarked @isiah’s while-loop test-case vs str.split vs str.replace for > regexp counting on jsperf.com [1], and the results were surprising (for me). > > benchmarks using 1mb random ascii-string from fastest to slowest. > 1. (fastest - 1,700 runs/sec) regexp-counting with > ```largeCode.split(/\n/).length - 1``` > 2. (40% slower - 1000 runs/sec) regexp-counting with ```while-loop (/n/g)``` > 3. (60% slower - 700 runs/sec) regexp-counting with > ```largeCode.replace((/[^\n]+/g), "").length``` > > looks like the go-to design-pattern for counting-regexp is > ```str.split(<regexp>).length - 1``` > > [1] regexp counting 2 > https://jsperf.com/regexp-counting-2 > > On 13 Jan 2019, at 9:15 PM, Isiah Meadows <[email protected]> wrote: > > If performance is an issue, regular expressions are likely to be too slow to > begin with. But you could always do this to count the number of lines in a > particular string: > > ```js > var count = 0 > var re = /\n|\r\n?/g > while (re.test(str)) count++ > console.log(count) > ``` > > Given it's already this easy to iterate something with a regexp, I'm not > convinced it's necessary to add this property/method. > On Sat, Jan 12, 2019 at 17:29 kai zhu <[email protected]> wrote: >> >> a common use-case i have is counting newlines in largish (> 200kb) >> embedded-js files, like this real-world example [1]. ultimately meant for >> line-number-preservation purposes in auto-lint/auto-prettify tasks (which >> have been getting slower due to complexity). >> >> would a new RegExp count-method like ```(/\n/g).count(largeCode)``` be >> significantly more efficient than existing ```largeCode.split("\n").length - >> 1``` or ```largeCode.replace((/[^\n]+/g), "").length```? >> >> -kai >> >> [1] calculating and reproducing line-number offsets when linting/autofixing >> files >> https://github.com/kaizhu256/node-utility2/blob/2018.12.30/lib.jslint.js#L7377 >> https://github.com/kaizhu256/node-utility2/blob/2018.12.30/lib.jslint.js#L7586 >> >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss > > _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
