const regex = /(("|]|}|\.|(\d|\.|-|:)\s*\d)\s*,|{)\s*(")?([^":\n]+?)(")?\s*:/g;
// Alternative syntax using RegExp constructor
// const regex = new RegExp('(("|]|}|\\.|(\\d|\\.|-|:)\\s*\\d)\\s*,|{)\\s*(")?([^":\\n]+?)(")?\\s*:', 'g')
const str = `{
type:"book",
author:["Willighagen, LG"],
editor:["Toos van Hoof","Karin Antoinette Henriette Majoor"],
date:
{
from:{
from:[1,2,2003],
}
}
,
print:3,
}`;
const subst = `$1"$5":`;
// 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