const regex = /(?sx)
(?|
０(?=.*(0))
|１(?=.*(1))
|２(?=.*(2))
|３(?=.*(3))
|４(?=.*(4))
|５(?=.*(5))
|６(?=.*(6))
|７(?=.*(7))
|８(?=.*(8))
|９(?=.*(9))
)/gs;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('(?sx)
(?|
０(?=.*(0))
|１(?=.*(1))
|２(?=.*(2))
|３(?=.*(3))
|４(?=.*(4))
|５(?=.*(5))
|６(?=.*(6))
|７(?=.*(7))
|８(?=.*(8))
|９(?=.*(9))
)', 'gs')
const str = `０ zero
１ ichi
２ ni
３ san
４ shi
５ go
６ roku
７ shichi
８ hachi
９ kyuu
0123456789`;
const subst = `\1`;
// The substituted value will be contained in the result variable
const result = str.replace(regex, subst);
console.log('Substitution result: ', result);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions