.. | ||
data | ||
LICENSE-MIT.txt | ||
package.json | ||
README.md | ||
rewrite-pattern.js |
regexpu-core
regexpu is a source code transpiler that enables the use of ES6 Unicode regular expressions in JavaScript-of-today (ES5).
regexpu-core contains regexpu’s core functionality, i.e. rewritePattern(pattern, flag)
, which enables rewriting regular expressions that make use of the ES6 u
flag into equivalent ES5-compatible regular expression patterns.
Installation
To use regexpu-core programmatically, install it as a dependency via npm:
npm install regexpu-core --save
Then, require
it:
const rewritePattern = require('regexpu-core');
API
This module exports a single function named rewritePattern
.
rewritePattern(pattern, flags, options)
This function takes a string that represents a regular expression pattern as well as a string representing its flags, and returns an ES5-compatible version of the pattern.
rewritePattern('foo.bar', 'u');
// → 'foo(?:[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uD7FF\\uDC00-\\uFFFF]|[\\uD800-\\uDBFF][\\uDC00-\\uDFFF]|[\\uD800-\\uDBFF])bar'
rewritePattern('[\\u{1D306}-\\u{1D308}a-z]', 'u');
// → '(?:[a-z]|\\uD834[\\uDF06-\\uDF08])'
rewritePattern('[\\u{1D306}-\\u{1D308}a-z]', 'ui');
// → '(?:[a-z\\u017F\\u212A]|\\uD834[\\uDF06-\\uDF08])'
regexpu-core can rewrite non-ES6 regular expressions too, which is useful to demonstrate how their behavior changes once the u
and i
flags are added:
// In ES5, the dot operator only matches BMP symbols:
rewritePattern('foo.bar');
// → 'foo(?:[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uFFFF])bar'
// But with the ES6 `u` flag, it matches astral symbols too:
rewritePattern('foo.bar', 'u');
// → 'foo(?:[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uD7FF\\uDC00-\\uFFFF]|[\\uD800-\\uDBFF][\\uDC00-\\uDFFF]|[\\uD800-\\uDBFF])bar'
The optional options
argument recognizes the following properties:
dotAllFlag
(default: false
)
Setting this option to true
enables experimental support for the s
(dotAll
) flag.
rewritePattern('.');
// → '[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uFFFF]'
rewritePattern('.', '', {
'dotAllFlag': true
});
// → '[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uFFFF]'
rewritePattern('.', 's', {
'dotAllFlag': true
});
// → '[\\0-\\uFFFF]'
rewritePattern('.', 'su', {
'dotAllFlag': true
});
// → '(?:[\\0-\\uD7FF\\uE000-\\uFFFF]|[\\uD800-\\uDBFF][\\uDC00-\\uDFFF]|[\\uD800-\\uDBFF](?![\\uDC00-\\uDFFF])|(?:[^\\uD800-\\uDBFF]|^)[\\uDC00-\\uDFFF])'
unicodePropertyEscape
(default: false
)
Setting this option to true
enables experimental support for Unicode property escapes:
rewritePattern('\\p{Script_Extensions=Anatolian_Hieroglyphs}', 'u', {
'unicodePropertyEscape': true
});
// → '(?:\\uD811[\\uDC00-\\uDE46])'
lookbehind
(default: false
)
Setting this option to true
enables experimental support for lookbehind assertions.
rewritePattern('(?<=.)a', '', {
'lookbehind': true
});
// → '(?<=[\\0-\\t\\x0B\\f\\x0E-\\u2027\\u202A-\\uFFFF])a'
namedGroup
(default: false
)
Setting this option to true
enables experimental support for named capture groups.
rewritePattern('(?<name>.)\k<name>', '', {
'namedGroups': true
});
// → '(.)\1'
onNamedGroup
This option is a function that gets called when a named capture group is found. It receives two parameters: the name of the group, and its index.
rewritePattern('(?<name>.)\k<name>', '', {
'namedGroups': true,
onNamedGroup(name, index) {
console.log(name, index);
// → 'name', 1
}
});
useUnicodeFlag
(default: false
)
Setting this option to true
enables the use of Unicode code point escapes of the form \u{…}
. Note that in regular expressions, such escape sequences only work correctly when the ES6 u
flag is set. Enabling this setting often results in more compact output, although there are cases (such as \p{Lu}
) where it actually increases the output size.
rewritePattern('\\p{Script_Extensions=Anatolian_Hieroglyphs}', 'u', {
'unicodePropertyEscape': true,
'useUnicodeFlag': true
});
// → '[\\u{14400}-\\u{14646}]'
Author
Mathias Bynens |
License
regexpu-core is available under the MIT license.