when I pass an empty string into includes("") will it always return true?

Question

So, I am testing the JS includes() method, so I created a search input field, where I can search through the notes I created with live rerendering. Now my question is: When I pass no searchtext at all, all the notes are shown, but when I enter a character or a word, the notes get filtered right away. Example code:

const filters = {
  searchText: ''
}

// Render application notes
const renderNotes = (notes, filters) => {
  const filteredNotes = notes.filter((note) => {

    return note.title.toLowerCase().includes(filters.searchText.toLowerCase())
  })
  document.querySelector('#notes').innerHTML = ''

  filteredNotes.forEach((note) => {
    const noteEl = generateNoteDOM(note)
    document.querySelector('#notes').appendChild(noteEl)
  })
}

I understand from this, that true is always returned in such a case.. Would appreciate any clarification to this subject!

Thanks!

Answer 1

The .includes() function has to match the functionality of .indexOf() for consistency, and .indexOf() always matches the empty string in any target string. From MDN:

An empty string searchValue will match at any index between 0 and str.length.

It's a little counter-intuitive, but consider this:

var str = "something";
console.log(str.includes("")); // Imagine this returns false ...
str += "";
console.log(str.includes("")); // !!