benchmarked @isiah’s while-loop test-case vs str.split vs str.replace for regexp counting on jsperf.com <http://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] > <mailto:[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#L7377> > https://github.com/kaizhu256/node-utility2/blob/2018.12.30/lib.jslint.js#L7586 > > <https://github.com/kaizhu256/node-utility2/blob/2018.12.30/lib.jslint.js#L7586> > > _______________________________________________ > es-discuss mailing list > [email protected] <mailto:[email protected]> > https://mail.mozilla.org/listinfo/es-discuss > <https://mail.mozilla.org/listinfo/es-discuss>
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