JavaScript String Search Methods

Searching for substrings within strings is a common task in JavaScript. The language provides several methods to locate and extract parts of a string based on search criteria. This article covers the primary string search methods available in JavaScript, including indexOf(), lastIndexOf(), includes(), startsWith(), and endsWith().

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1. indexOf()

The indexOf() method returns the index of the first occurrence of a specified substring. If the substring is not found, it returns -1.

// Example
const str = 'Hello, world!';
console.log(str.indexOf('world')); // Output: 7
console.log(str.indexOf('foo')); // Output: -1

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2. lastIndexOf()

The lastIndexOf() method returns the index of the last occurrence of a specified substring. If the substring is not found, it returns -1.

// Example
const str = 'Hello, world! World is big!';
console.log(str.lastIndexOf('world')); // Output: 7 (case-sensitive)
console.log(str.lastIndexOf('World')); // Output: 20
console.log(str.lastIndexOf('foo')); // Output: -1

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3. includes()

The includes() method checks if a string contains a specified substring. It returns true if the substring is found and false otherwise. It is case-sensitive.

// Example
const str = 'Hello, world!';
console.log(str.includes('world')); // Output: true
console.log(str.includes('foo')); // Output: false

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4. startsWith()

The startsWith() method checks if a string starts with a specified substring. It returns true if it does and false otherwise. It is case-sensitive.

// Example
const str = 'Hello, world!';
console.log(str.startsWith('Hello')); // Output: true
console.log(str.startsWith('world')); // Output: false

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5. endsWith()

The endsWith() method checks if a string ends with a specified substring. It returns true if it does and false otherwise. It is case-sensitive.

// Example
const str = 'Hello, world!';
console.log(str.endsWith('world!')); // Output: true
console.log(str.endsWith('Hello')); // Output: false

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Conclusion

JavaScript offers several methods for searching within strings. The indexOf() and lastIndexOf() methods provide positions of substrings, while includes(), startsWith(), and endsWith() are useful for checking the presence and position of substrings in a more straightforward manner. Mastering these methods will help you efficiently handle and manipulate string data in your JavaScript projects.