Symbol.search

class Search1 {
  constructor(value) {
    this.value = value;
  }
  [Symbol.search](string) {
    return string.indexOf(this.value);
  }
}
console.log("foobar".search(new Search1("bar")));
// Expected output: 3

class CaseInsensitiveSearch {
  constructor(value) {
    this.value = value.toLowerCase();
  }
  [Symbol.search](string) {
    return string.toLowerCase().indexOf(this.value);
  }
}
console.log("foobar".search(new CaseInsensitiveSearch("BaR"))); // 3