Then how could you find `undefined` in an array? That's a real use case too.
In your A example, I'd represent that as: ``` var paths = files.map(file => path.resolve(base, file)); var found = paths.find(filePath => fs.existsSync(filePath)); ``` … and then `found` would be the resolved path you're looking for. On Tue, Apr 7, 2015 at 11:41 AM, 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 >
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