The user's code… Trying to parse "" will also throw with JSON; !!"false " is true; host objects (or whatever they're called now) such as document.all.
Unsubscribing. Not sure why I didn't earlier… I need to stay a code-free user. :-) On Thu, Mar 16, 2017 at 7:08 PM, 段垚 <[email protected]> wrote: > > > 在 2017/3/17 5:03, Ben Newman 写道: > > Just to check my understanding, would > > Boolean.parseBoolean = function (value) { > return !! (value && JSON.parse(String(value))); > }; > > be a reasonable polyfill for your proposed function? > > This implemention throws for invalid JSON syntax and is case-sensitive > (Java's counterpart is case-insensitive). Is this better? > ``` > Boolean.parseBoolean = function (value) { > return !(!value || /^false$/i.test('' + value)); > }; > ``` > > However I'm not sure this is widely useful. If the value is not from JSON, > there are a lot of alternatives for 'true|false', e.g. 'yes|no', 'on|off', > or 'T|F', and different rules for casing/empty value/invalid syntax. So > it's better to do this in users' code. > > > > This would definitely be useful for parsing `process.env.*` environment > variables in Node! > > Ben > > On Thu, Mar 16, 2017 at 4:55 PM Dmitry Soshnikov < > [email protected]> wrote: > >> Similar to `Number.parseInt`, the `Boolean.parseBooelan` might be useful >> for "boolean strings" retrieved from some string-based storages, which do >> not support other types at serialization. >> >> ``` >> Boolean.parseBoolean('true'); // true >> Boolean.parseBoolean('false'); // false >> ``` >> >> This is to contrast current: >> >> ``` >> Boolean('false'); // true >> ``` >> >> In JS people do today: >> >> ``` >> let shouldRefresh = (data.shouldRefresh === 'true'); >> ``` >> >> Other parsing results: >> >> ``` >> Boolean.parseBoolean('1'); // true >> Boolean.parseBoolean(1); // true >> Boolean.parseBoolean(<not-falsey>); // true >> Boolean.parseBoolean(true); // true >> >> // Falsey: >> Boolean.parseBoolean('0'); // false >> Boolean.parseBoolean(''); // false >> Boolean.parseBoolean(false); // false >> ``` >> >> The API, and the results are from Java's corresponding >> `Boolean.parseBoolean` method: https://docs.oracle. >> com/javase/7/docs/api/java/lang/Boolean.html# >> parseBoolean(java.lang.String). >> >> Dmitry >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> > > > _______________________________________________ > es-discuss mailing > [email protected]https://mail.mozilla.org/listinfo/es-discuss > > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > > -- Garrett Guitar Videos https://www.youtube.com/channel/UCY_uK9hur86KEuiG8s7yvWw @xkit
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