valid regex generator

const fc = require('fast-check'); const testIt = (arb) => console.log(fc.sample(arb, 5)); const regexCharacterArb = fc.fullUnicode().filter(c => !'^$\.*+?()[]{}|'.includes(c)); //testIt(regexCharacterArb); const hexaNotationArb = fc.nat(255).map(n => '\\x' + Number(n).toString(16).padStart(2, '0')); //testIt(hexaNotationArb); const unicodeNotationArb = fc.oneof( fc.unicode().map(c => '\\u' + Number(c.codePointAt(0)).toString(16).padStart(4, '0')), fc.fullUnicode().map(c => '\\u{' + Number(c.codePointAt(0)).toString(16).padStart(4, '0') + '}')); //testIt(unicodeNotationArb); const controlEscapeArb = fc.constantFrom('\\f','\\n','\\r','\\t','\\v'); //testIt(controlEscapeArb); const controlLetterArb = fc.constantFrom( '\\cA','\\cB','\\cC','\\cD','\\cE','\\cF', '\\cG','\\cH','\\cI','\\cJ','\\cK','\\cL', '\\cM','\\cN','\\cO','\\cP','\\cQ','\\cR', '\\cS','\\cT','\\cU','\\cV','\\cW','\\cX', '\\cY','\\cZ'); //testIt(controlLetterArb); const characterClassEscapeArb = fc.constantFrom('\\d','\\D','\\s','\\S','\\w','\\W','.'); // and . //testIt(characterClassEscapeArb); const escapedSyntaxCharacterArb = fc.constantFrom( '\\^','\\#x27;,'\\\\','\\.','\\*','\\+','\\?', '\\(','\\)','\\[','\\]','\\{','\\}','\\|'); //testIt(escapedSyntaxCharacterArb); const variousOneCharacterArb = fc.oneof(regexCharacterArb, characterClassEscapeArb, escapedSyntaxCharacterArb, hexaNotationArb, unicodeNotationArb, controlEscapeArb, controlLetterArb); const bracketRegexArb = fc.tuple( fc.boolean(), fc.stringOf(fc.oneof( variousOneCharacterArb.filter(c => c !== '-' && c !== '\\x2d' && c !== '\\u002d' && c !== '\\u{002d}'), fc.tuple(regexCharacterArb, regexCharacterArb) .filter(([a, b]) => a.codePointAt(0) !== 0x2d && b.codePointAt(0) !== 0x2d) .map(([a, b]) => a.codePointAt(0) < b.codePointAt(0) ? [a,b]: [b,a]) .map(([a, b]) => `${a}-${b}`) )), fc.boolean() ).map(([startDash, s, endDash]) => `[${startDash?'-':''}${s}${endDash?'-':''}]`) //testIt(bracketRegexArb); const noCaptureArb = fc.array(fc.oneof(bracketRegexArb, fc.stringOf(variousOneCharacterArb))) .map(content => `${content.join('')}`); //testIt(noCaptureArb); const braceRegexArb = fc.array(noCaptureArb) .map(content => `(${content.join('|')})`); //testIt(braceRegexArb); const regexArb = fc.array(fc.oneof(braceRegexArb, bracketRegexArb, fc.stringOf(variousOneCharacterArb))) .map(content => `${content.join('|')}`); testIt(regexArb); fc.assert( fc.property( regexArb, pattern => { new RegExp(pattern, 'u'); } // does not crash - ie. valid regex ), {numRuns: 10000} );