In this lesson, you'll learn about various methods to search for substrings within a string in JavaScript, which are useful for checking the presence and position of text.

Finding Substrings in a String

There are multiple ways to look for a substring within a string in JavaScript. Let's explore some of the most common methods.

str.indexOf()

The first method is . It searches for the in , starting from the given position , and returns the position where the match was found or if nothing can be found.

For instance:

const exampleString = 'I love ducks, he said, ducks are great!';

console.log(exampleString.indexOf('ducks')); // 7
console.log(exampleString.indexOf('Ducks')); // -1

The optional second parameter allows us to search starting from the given position. For instance, the first occurrence of is at position . To look for the next occurrence, let’s start the search from position :

console.log(exampleString.indexOf('ducks', 8)); // 23

str.lastIndexOf()

is similar to , but it searches from the end of a string to its beginning.

console.log(exampleString.lastIndexOf('ducks')); // 23

includes()

If you're just interested in whether a string contains a substring, and not its position, you can use . It simply returns or .

console.log(exampleString.includes('ducks')); // true

As with the method, the optional second argument of is the position to start searching from.

str.startsWith() & str.endsWith()

The methods and check if a string starts or ends with a specific substring:

console.log(exampleString.startsWith('I')); // true
console.log(exampleString.endsWith('ducks')); // false

These methods provide powerful ways to search and check for substrings within strings, making it easier to manipulate and analyze text in JavaScript.

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