find a solution for JavaScript Regex SyntaxError

the following regex would work

(?<=\w+\. ?)\w+

So basically +., + is a qualifier that actually for one or more of the preceding characters or group which is making an issue

+.( )

I tried to change it to make it run :

const regex = /(\w{2,}\.( ){1,})|(, \w+)/g;

I tried to modify your regex, simply by using word characters and capturing them in a group and added optional checking on dot

const regex = /^\w+[.\s]\s*|\.$/g;

const nama = "DR. Tida";
const nama1 = "prof. Sina.";
const regex = /^\w+[.\s]\s*|\.$/g;
console.log(nama.replace(regex,""));
console.log(nama1.replace(regex,""));

Just mentioning flexible regex where you can use the group as if you want the first name of the last name by using $1 or $2

const regex = /(\w+)\.\s(\w+)(\.?)/;

const nama = "DR. Tida";
const nama1 = "prof. Sina.";

const regex = /(\w+)\.\s(\w+)(\.?)/g;
console.log(nama.replace(regex,"$2"));
console.log(nama1.replace(regex,"$2"));

Javascript does not support possessive quantifier like \w{2,}+ but apart from that your pattern will not give you the desired results after replacing.

Note that the space ( ) does not have to be between parenthesis to make it a group, you have to escape the dot \. to match it literally and {1,} can be written as +

What you might do is repeat matching 2 or more word characters followed by a dot and 1+ spaces OR match 1 or more times a non word character except for a whitespace char.

In the replacement use an empty string.

(?:\w{2,}\.[^\S\n]+)+|[^\w\s]+

See a regex 101 demo.

const regex = /(?:\w{2,}\.[^\S\n]+)+|[^\w\s]+/g;
const s = `DR. Tida.
prof. Sina.
DR. prof. Tida.`;

console.log(s.replace(regex, ""));

Although this part \w{2,}\. can obviously match more than just titles.

You can also list using an alternation what you want to remove to make it more specific:

(?:\b(?:DR|prof)\.[^\S\n]+)+|[^\w\s]+

See another regex101 demo