@rbxts/jsnatives

includes

Determines whether a string contains a specified substring.

Signature

function includes(str: string, substring: PatternAdmissible, position?: NumericAdmissible): boolean

Description

The includes function checks if a string contains a specified substring. It returns true if the string contains the specified substring, and false otherwise. The search is case-sensitive.

Parameters

str: The string to search within.
substring: The value to search for. Can be a string, number, or boolean.
position (optional): The position within the string to start the search. Default is 0. If a string is provided, it will be converted to a number.

Return value

true if the string contains the specified substring.
false if the substring is not found.

Examples

Basic usage

// Check if a string contains a substring
const hasWorld = String.includes("Hello world", "world");
print(hasWorld); // Outputs: true

const hasHello = String.includes("Hello world", "Hello");
print(hasHello); // Outputs: true

const hasFoo = String.includes("Hello world", "foo");
print(hasFoo); // Outputs: false

With starting position

// Start searching from position 6
const text = "Hello world";
const hasO = String.includes(text, "o", 6);
print(hasO); // Outputs: true (finds the 'o' in "world")

const hasE = String.includes(text, "e", 2);
print(hasE); // Outputs: false (the 'e' is at position 1, before the starting position)

Using non-string values

// Searching for a number (converted to string)
const hasNumber = String.includes("The answer is 42", 42);
print(hasNumber); // Outputs: true

// Searching for a boolean (converted to string)
const hasBoolean = String.includes("Set value to true", true);
print(hasBoolean); // Outputs: true

Practical applications

// Check if an email is valid (very simple check)
function isValidEmail(email: string): boolean {
  return String.includes(email, "@") && String.includes(email, ".");
}

print(isValidEmail("user@example.com")); // Outputs: true
print(isValidEmail("invalid-email")); // Outputs: false

// Check if a string contains any of several substrings
function containsAny(text: string, ...substrings: string[]): boolean {
  for (const substring of substrings) {
    if (String.includes(text, substring)) {
      return true;
    }
  }
  return false;
}

const containsBadWord = containsAny(
  "This is a nice message",
  "bad", "offensive", "inappropriate"
);
print(containsBadWord); // Outputs: false