JavaScript String Search

In JavaScript, there are several methods available to search for a substring or pattern within a string. These methods help you locate specific text, check for the presence of text, or retrieve matches based on patterns.

JavaScript String Search Methods

• indexOf(): Finds the first occurrence of a value.
• lastIndexOf(): Finds the last occurrence of a value.
• includes(): Checks if a string contains a value.
• search(): Searches for a match and returns the position.
• match(): Returns an array of matches against a regular expression.
• matchAll(): Returns an iterator of all matches.
• startsWith(): Checks if a string starts with specified characters.
• endsWith(): Checks if a string ends with specified characters.

1. indexOf()

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

let text = 'Hello, World!';
let position = text.indexOf('World');
console.log(position);  // Output: 7

Key Points:

• It is case-sensitive.
• Returns -1 if the value is not found.

2. lastIndexOf()

The lastIndexOf() method returns the index of the last occurrence of a specified value in a string. It searches the string backward.

let text = 'Hello, World! World!';
let position = text.lastIndexOf('World');
console.log(position);  // Output: 14

Key Points:

• It is case-sensitive.
• Returns -1 if the value is not found.

3. includes()

The includes() method checks if a string contains a specified value. It returns true or false.

let text = 'Hello, World!';
let result = text.includes('World');
console.log(result);  // Output: true

Key Points:

• It is case-sensitive.
• Returns a boolean value.

4. search()

The search() method searches a string for a specified value or regular expression and returns the position of the first match.

let text = 'Hello, World!';
let position = text.search('World');
console.log(position);  // Output: 7

Key Points:

• You can use a regular expression for more complex searches.
• Returns -1 if the value is not found.

5. match()

The match() method searches a string for a match against a regular expression and returns the matches as an array.

let text = 'The rain in Spain stays mainly in the plain';
let matches = text.match(/ain/g);
console.log(matches);  // Output: ['ain', 'ain', 'ain']

Key Points:

• Useful for extracting matched patterns.
• Returns null if no matches are found.

6. matchAll()

The matchAll() method returns an iterator of all results matching a string against a regular expression, including capturing groups.

let text = 'The rain in Spain stays mainly in the plain';
let matches = text.matchAll(/ain/g);
for (let match of matches) {
    console.log(match);
}

Key Points:

• Provides detailed information about matches, including groups.
• Returns an iterator.

7. startsWith()

The startsWith() method checks if a string starts with specified characters and returns true or false.

let text = 'Hello, World!';
let result = text.startsWith('Hello');
console.log(result);  // Output: true

8. endsWith()

The endsWith() method checks if a string ends with specified characters and returns true or false.

let text = 'Hello, World!';
let result = text.endsWith('World!');
console.log(result);  // Output: true

Summary

These methods are essential for searching and manipulating strings in JavaScript, providing flexibility and efficiency in handling text-based operations.