Generate a random string match a given regular expression, suitable for mocking strings.
npm install reregexp 
Generate a matched string with a given regular expression, it's useful if you want to mock some strings from a regexp rule. It strictly abide by the standard javascript regex rule, but you still need pay attentions with the Special cases.
- Support named capture group, e.g. (?, and also allowing to override it by expose a config field namedGroupConf.
- Support unicode property class \p{Lu} by setting the static UPCFactory handle, see the example for more details.
- Support u flag, so you can use unicode ranges.
- Allow you get the capture group values.
``bash`npm
npm install --save reregexpor yarn
yarn add reregexp
`javascript
// Commonjs module
const ReRegExp = require('reregexp').default;
// ESM module
// since v1.6.1
import ReRegExp from 'reregexp';
// before v1.6.1
import re from 'reregexp';
const ReRegExp = re.default;
// For the first parameter of the constructor
// You can use a regex literal or a RegExp string
// if you need use some features that are not well supported by all browsers
// such as a named group, you should always choose a RegExp string
// Example 1: use group reference
const r1 = new ReRegExp(/([a-z0-9]{3})_\1/);
r1.build(); // => 'a2z_a2z' '13d_13d'
// Example 2: use named group
const r2 = new ReRegExp(/(?
r2.build(); // => 'b5_b5_b5' '9_9_9'
// Example 3: use named group and with namedGroupConf config
// it will use the string in the config insteadof the string that will generated by the named group
// of course, it will trigger an error if the string in config not match the rule of named group.
const r3 = new ReRegExp('/(a)\\1(?
namedGroupConf: {
override: ['cc', 'dd'],
},
});
r3.build(); // => "aabbcc" "aabbdd"
// Example 4: use a character set
const r4 = new ReRegExp(/[^\w\W]+/);
r4.build(); // will throw error, because the [^\w\W] will match nothing.
// Example 5: also a character set with negative operator
const r5 = new ReRegExp(/[^a-zA-Z0-9_\W]/);
r5.build(); // will throw error, this is the same as [^\w\W]
// Example 6: with the i flag, ignore the case.
const r6 = new ReRegExp(/[a-z]{3}/i);
r6.build(); // => 'bZD' 'Poe'
// Example 7: with the u flag, e.g. make some chinese characters.
const r7 = new ReRegExp('/[\\u{4e00}-\\u{9fcc}]{5,10}/u');
r7.build(); // => '偤豄酌菵呑', '孜垟与醽奚衜踆猠'
// Example 8: set a global maxRepeat when use quantifier such as '*' and '+'.
ReRegExp.maxRepeat = 10;
const r8 = new ReRegExp(/a*/);
r8.build(); // => 'aaaaaaa', 'a' will repeated at most 10 times.
// Example 9: use a maxRepeat in constructor config, it will override maxRepeat of the global.
const r9 = new ReRegExp(/a*/, {
maxRepeat: 20,
});
r9.build(); // => 'aaaaaaaaaaaaaa', 'a' will repeated at most 20 times
// Example 10: use a extractSetAverage config for character sets.
const r10 = new ReRegExp(/[\Wa-z]/, {
// \W will extract as all the characters match \W, a-z now doesn't have the same chance as \W
extractSetAverage: true,
});
// Example 11: use a capture config if cared about the capture datacapture
const r11 = new ReRegExp(/(aa?)b(?
capture: true, // if you cared about the group capture data, set the config true
});
r11.build(); // => 'abc'
console.log(r11.$1); // => 'a'
console.log(r11.$2); // => 'c'
console.log(r11.groups); // => {named: 'c'}
// Example 12: use the unicode property class by setting the UPCFactory
ReRegExp.UPCFactory = (data: UPCData) => {
/*
UPCData: {
negate: boolean; // if the symbol is 'P'
short: boolean; // take '\pL' as a short for '\p{Letter}'
key?: string; // if has a unicode property name, such as
value: string; // unicode property value, binary or non-binary
}
*/
return {
generate(){
return 'x'; // return an object that has a method.UPCFactory
}
}
};
const r12 = new ReRegExp('/\\p{Lu}/u');
console.log(r12.build()); // => 'x', should handle in the method.`
`typescript`
// The meaning of the config fields can seen in the examples.
{
maxRepeat?: number;
namedGroupConf?: {
[index: string]: string[]|boolean;
};
extractSetAverage?: boolean;
capture?: boolean;
}
- i ignore case, /[a-z]/i is same as /[a-zA-Z]/
- u unicode flag
- s dot all flag
the flags g m y will ignore.
.build()
build a string that match the regexp.
.info()
get a regexp parsed queues, flags, lastRule after remove named captures.
`javascript`
{
rule: '',
context: '',
flags: [],
lastRule: '',
queues: [],
}
1. ^ $ the start,end anchors will be ignored.(?=)
2. (?!) (?<=) (? the regexp lookhead,lookbehind will throw an error when run build().
3. \b \B will be ignored.
1. /\1(o)/ the capture group \1 will match null, the build() will just output o, and /^\1(o)$/.test('o') === true
2. /(o)\1\2/ the capture group \2 will treated as code point of unicode. so the build() will output oo\u0002. /^(o)\1\2$/.test('oo\u0002') === true
3. /(o\1)/ the capture group \1 will match null, build() will output o, /^(o\1)$/.test('o') === true
4. /[]/ empty character class, the build() method will throw an error, because no character will match it.
5. /[^]/ negative empty character class, the build() method will output any character.
6. /[^\w\W]/ for the negative charsets, if all the characters are eliminated, the build() will throw an error. the same such as /[^a-zA-Z0-9_\W]/、/[^\s\S]/`...
Welcome to report to us with issue if you meet any question or bug.