String.prototype.includes()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2015.

The includes() method of String values performs a case-sensitive search to determine whether a given string may be found within this string, returning true or false as appropriate.

Try it

const sentence = "The quick brown fox jumps over the lazy dog.";

const word = "fox";

console.log(
  `The word "${word}" ${
    sentence.includes(word) ? "is" : "is not"
  } in the sentence`,
);
// Expected output: "The word "fox" is in the sentence"

A string to be searched for within str. Cannot be a regex. All values that are not regexes are coerced to strings, so omitting it or passing undefined causes includes() to search for the string "undefined", which is rarely what you want.

position Optional

The position within the string at which to begin searching for searchString. (Defaults to 0.)

You can work around this constraint by transforming both the original string and the search string to all lowercase:

"Blue Whale".toLowerCase().includes("blue"); // returns true

Examples

Using includes()

js
const str = "To be, or not to be, that is the question.";

console.log(str.includes("To be")); // true
console.log(str.includes("question")); // true
console.log(str.includes("nonexistent")); // false
console.log(str.includes("To be", 1)); // false
console.log(str.includes("TO BE")); // false
console.log(str.includes("")); // true