const regex = /(?s)\b(\w+)\b(?=.*:\1=(\w+)\b)/gs;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('(?s)\\b(\\w+)\\b(?=.*:\\1=(\\w+)\\b)', 'gs')
const str = `blue cheese, a red nose.
Dictionary:blue=bleu:red=rouge:green=vert`;
const subst = `\2`;
// 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