I have to modify a script. I see this often _.escape( does it mean the remove the escape or add escape or what is it ? I want to learn

Likely lodash. https://lodash.com/docs/4.17.15#escape

its a library function, so it would depend on the library two common JS libraries that use that _.method are underscore.js and lodash.js... which have a lot of overlap but it replaces & with amp; so its specifically for writing html