How Can I Efficiently Check for Substrings in JavaScript?

Finding Substrings in JavaScript

Many programming languages provide a straightforward method for checking whether a string contains a particular substring. However, despite expectations, the JavaScript language does not have a dedicated String.contains() method.

Finding a Solution

For JavaScript developers, there are several alternatives for detecting substrings:

String.prototype.includes (ES6 ):

Introduced in ECMAScript 6, this method returns a boolean indicating whether the string contains the specified substring.

const string = "foo";
const substring = "oo";

console.log(string.includes(substring)); // true

String.prototype.indexOf:

This method returns the first index of the substring within the string, or -1 if it's not found. You can check if the index is greater than or equal to 0 to determine the substring's existence.

const string = "foo";
const substring = "oo";

const index = string.indexOf(substring);
console.log(index !== -1); // true

String.prototype.search:

Similar to indexOf, but performs a regular expression search. It returns the first matching index or -1 if not found. However, since substrings are not regular expressions by default, you'll need to prefix the substring with .

const string = "foo";
const substring = "oo";

const index = string.search(`\${substring}`);
console.log(index !== -1); // true

String.prototype.match:

This method returns an array of matches found within the string. If the array has at least one item, the substring exists.

const string = "foo";
const substring = "oo";

const matches = string.match(substring);
console.log(matches.length > 0); // true

Conclusion:

While JavaScript doesn't have a dedicated contains method, developers have several viable options for checking substrings, each with its own performance characteristics and suitability for specific use cases.

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