Cannot set property 'lastIndex' of undefined

[HamedFathi]

I wrote your basic sample in VSCode

const Lexer = require('flex-js');
var lexer = new Lexer();
// options
lexer.setIgnoreCase(true);  // does not make sense for this scanner, just for reference
// definitions
lexer.addDefinition('DIGIT', /[0-9]/);
// rules
lexer.addRule(/{DIGIT}+\.{DIGIT}+/, function (lexer) {
  console.log('Found float: ' + lexer.text);
});
lexer.addRule(/\s+/);
// code
lexer.setSource('1.2 3.4 5.6');
lexer.lex();

and I got an error

...\node_modules\flex-js\src\Lexer.js:647
  re.lastIndex = this.index;
               ^

TypeError: Cannot set property 'lastIndex' of undefined
    at Lexer.execRegExp (...\node_modules\flex-js\src\Lexer.js:647:16)

I am not sure what is the problem but I handled the error with a line of code

  if (!re) return undefined;

Can you guide me?

[sormy]

What OS and NodeJS version are you using?
Provided example works without issues on Node v12.5.0 (macOS)

[sormy]

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