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Diffstat (limited to 'node_modules/js-tokens/README.md')
| -rw-r--r-- | node_modules/js-tokens/README.md | 32 |
1 files changed, 25 insertions, 7 deletions
diff --git a/node_modules/js-tokens/README.md b/node_modules/js-tokens/README.md index 5c93a8885..00cdf1634 100644 --- a/node_modules/js-tokens/README.md +++ b/node_modules/js-tokens/README.md @@ -73,14 +73,13 @@ Whitespace includes both line terminators and other whitespace. ECMAScript support ================== -The intention is to always support the latest stable ECMAScript version. +The intention is to always support the latest ECMAScript version whose feature +set has been finalized. If adding support for a newer version requires changes, a new version with a major verion bump will be released. -Currently, [ECMAScript 2017] is supported. - -[ECMAScript 2017]: https://www.ecma-international.org/ecma-262/8.0/index.html +Currently, ECMAScript 2018 is supported. Invalid code handling @@ -100,7 +99,8 @@ inside the regex. Invalid ASCII characters have their own capturing group. Invalid non-ASCII characters are treated as names, to simplify the matching of -names (except unicode spaces which are treated as whitespace). +names (except unicode spaces which are treated as whitespace). Note: See also +the [ES2018](#es2018) section. Regex literals may contain invalid regex syntax. They are still matched as regex literals. They may also contain repeated regex flags, to keep the regex @@ -144,7 +144,8 @@ var regex = / 2/g A human can easily understand that in the `number` line we’re dealing with division, and in the `regex` line we’re dealing with a regex literal. How come? Because humans can look at the whole code to put the `/` characters in context. -A JavaScript regex cannot. It only sees forwards. +A JavaScript regex cannot. It only sees forwards. (Well, ES2018 regexes can also +look backwards. See the [ES2018](#es2018) section). When the `jsTokens` regex scans throught the above, it will see the following at the end of both the `number` and `regex` rows: @@ -192,7 +193,7 @@ valid regex flag. I initially wanted to future-proof by allowing `[a-zA-Z]*` (any letter) as flags, but it is not worth it since it increases the amount of ambigous cases. So only the standard `g`, `m`, `i`, `y` and `u` flags are allowed. This means that the above example will be identified as division as -long as you don’t rename the `e` variable to some permutation of `gmiyu` 1 to 5 +long as you don’t rename the `e` variable to some permutation of `gmiyus` 1 to 6 characters long. Lastly, we can look _forward_ for information. @@ -215,6 +216,23 @@ If the end of a statement looks like a regex literal (even if it isn’t), it will be treated as one. Otherwise it should work as expected (if you write sane code). +### ES2018 ### + +ES2018 added some nice regex improvements to the language. + +- [Unicode property escapes] should allow telling names and invalid non-ASCII + characters apart without blowing up the regex size. +- [Lookbehind assertions] should allow matching telling division and regex + literals apart in more cases. +- [Named capture groups] might simplify some things. + +These things would be nice to do, but are not critical. They probably have to +wait until the oldest maintained Node.js LTS release supports those features. + +[Unicode property escapes]: http://2ality.com/2017/07/regexp-unicode-property-escapes.html +[Lookbehind assertions]: http://2ality.com/2017/05/regexp-lookbehind-assertions.html +[Named capture groups]: http://2ality.com/2017/05/regexp-named-capture-groups.html + License ======= |