Full-Text Search in Javascript

a few thousand records

This is not that much, have a look at the Full-Text Search in JavaScript with a demo of full-text search in 40k rows.

.indexOf()

JavaScript is a bit limited when it comes to text manipulation, but this will do the job.

Here is a pretty straightforward manual that is perfectly fitting to your question. Jekyll + lunr.js = Static websites with powerful full-text search using JavaScript

I have experience of building static web-pages with smaller amounts of data and usually, performance is the last issue on the way.

Using Fuse.js w/out Jquery

As you propably also want to have a fuzzy search nowadays. You could use a lib like Fuse.js (demo) to very easily search an array of (nested) objects - this should be as complicated as the "poor mans" approach, but way more effective

E.g. if you have an array ob objects:

[
  {
    "title": "Old Man's War",
    "author": "John Scalzi",
    "tags": ["fiction"]
  },
  {
    "title": "The Lock Artist",
    "author": "Steve",
    "tags": ["thriller"]
  }
]

To search simply use fuse.search('text') after initialization.

const options = {
  includeScore: true,
  // Search in `author` and in `tags` array
  keys: ['author', 'tags']
}

const fuse = new Fuse(list, options)

const result = fuse.search('OldMans War')

See the list of options to limit results.