Published Mar 21, 2022
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The .includes() method returns true if a given value is included in a string. Otherwise, it returns false.


string.includes(value, index=0);

The following parameters are used:

  • A case-sensitive value that is checked for inclusion in the array.
  • An optional index, defaulted to 0, that tells .includes() where to begin the check.

Here are some edge-cases to consider when using .includes():

  • It will not work if the provided index is greater than the length of the string. Instead, false will be returned.
  • If the index is less than or equal to 0, the entire string will be searched.


The .includes() method can be used in a few ways. First, it can be applied directly to a string:

console.log('Hello World!'.includes('World'));
// Output: true

It can also be used with a string value assigned to a variable:

const helloWorld = 'Hello World!';
// Output: false

The output above is false because .includes() is case-sensitive. The string literal world was checked for with a lowercase “w” rather than a capital “W” like in the helloWorld string.

Codebyte Example

In the example below, the .includes() method is applied three times to the myString variable, using a combination of optional parameters:

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