not sure if off topic but * you need a with statement to use lodash like that * ... the following ...
``` let found = first(filter( map(files, _ => path.resolve(base, _)), fs.existsSync )); ``` is a very wasteful pattern ... have you ever heard of `some` ? ``` let found; some(files, _ => fs.existsSync(found = path.resolve(base, _)) || (found = '') || false); ``` It could bring few alchemies in ;-) On Tue, Apr 7, 2015 at 9:14 PM, Alexander Jones <[email protected]> wrote: > You need lazy sequences aka iterators. They give you the rather optimal: > > let found = first(filter( > map(files, _ => path.resolve(base, _)), > fs.existsSync > )); > > Libs like lodash and lazy.js provide the bits you need, which are > actually fairly trivial to build on top of nice new ES6 iterators if you > want. > > Alex > > > On Tuesday, April 7, 2015, Martin Heidegger <[email protected]> > wrote: > >> I am probably very late to the game but I just read about harmonies >> “Array.prototype.find” and found that it might be worth considering a >> change in way it works. Its not a drastic change but it would break the >> compatibility to the current setup. I understand that the chances for this >> going through will be slim but since I would like to give it a shot anyways: >> >> Currently the API uses a callback function that has to return a boolean >> to identify the item that has been found. This is good because find & >> findIndex can use the same methods but it also has a drawback. >> >> Problem: Say you have a list of items that need to be processed before >> you know if you “found” the item. Then you will need to process the last >> item again since there is no way to “keep” the result (A) of the find >> method or you preprocess all items using map (B) that will require to >> process all the items even if the first one already matches. >> >> Example: >> >> (BASE) >> var files = [“main.md”, “backup.md”] >> var base = “/my/root" >> >> (A) >> // Specifies `path.resolve` on two places >> var found = files.find(function (file) { >> return fs.existsSync(path.resolve(base, file)) >> })) >> if (found) >> found = path.resolve(base, file) >> >> (B) >> // Runs `path.resolve` for all items >> var found = files.map(function (file) { >> return path.resolve(base, file) >> }).find(fs.existsSync) >> >> Proposal (C): I think it might be interesting to have a change of the >> signature so that the return value is not true/false but the value that >> actually will be returned (not undefined): >> >> (C) >> var found = files.find(function (file) { >> file = path.resolve(base, file) >> if(fs.existsSync(file)) >> return file >> }); >> >> This way the operations would be minimised, it is still few to write and >> it would make life a bit easier. >> >> yours >> Martin Heidegger >> _______________________________________________ >> 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 > >
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