Search a String for a Pattern in JavaScript

Searching strings for specific patterns is a common task in JavaScript. Strings are data types and are represented as a sequence of characters. Searching patterns means verifying the presence of a specific pattern in a given string. A pattern would be a specific word, specific characters, and so on.

JavaScript offers several powerful methods for pattern matching, such as inbuilt string methods and regular expressions. This article will guide you on how to search strings for specific patterns in JavaScript.

Table of contents

Searching strings for specific patterns in JavaScript can be done in the following ways:

• Using Inbuilt String Search Methods
• Using Regular Expressions

Using Inbuilt String Search Methods

Searching strings for a specific pattern can be simply implemented using inbuilt JavaScript methods.

• includes(): The includes() method determines whether a string contains the specified characters. It returns the boolean value. The following is a syntax for this:

stringName.includes("pattern");

indexOf() The indexOf() method returns the position of the first occurrence of a specified value in a string. The following is a syntax for this:

stringName.indexOf("pattern");

startsWith() and endsWith(): These methods check if a string begins or ends with a specific substring. The following is a syntax for this:

stringName.startsWith("character");
const isHtml = stringName.endsWith("character");

Example

The following uses string includes(), indexOf(), startWith(), and endWith() methods to search a string for a pattern in JavaScript.

const text = "Hello, welcome to the world of JavaScript!";

// Using includes()
const hasWelcome = text.includes("welcome");
console.log(`Includes "welcome": ${hasWelcome}`);

// Using indexOf()
const index = text.indexOf("world");
console.log(`Index of "world": ${index}`);

// Using startsWith()
const startsWithHello = text.startsWith("Hello");
console.log(`Starts with "Hello": ${startsWithHello}`);

// Using endsWith()
const endsWithScript = text.endsWith("JavaScript!");
console.log(`Ends with "JavaScript!": ${endsWithScript}`);

Output

Includes "welcome": true
Index of "world": 22
Starts with "Hello": true
Ends with "JavaScript!": true

Using Regular Expressions

A regular expression (RegExp) in JavaScript is an object that describes a pattern of characters. It can contain the alphabetical, numeric, and special characters. To search strings for a specific pattern, regular expressions can be used.

• String.match(): The match() method is one of the regular expression methods that returns an array of matches. The following is a syntax for this:

string.match( expression )

String.search(): The search() method is another regular expression methods that returns the index of the first match. The following is a syntax for this:

str.search( pattern )

Example

In the following example, the code demonstrates two ways to search for patterns in a string. The search() method finds the index of the word "world" in the text and logs it, while the match() method checks for the presence of the word "welcome" and logs the match if found, or indicates that no match was found.

const text = "Hello, welcome to the world of JavaScript!";

// Using search()
const searchPattern = /world/;
const searchIndex = text.search(searchPattern);
console.log(`Index of "world": ${searchIndex}`);

// Using match()
const matchPattern = /welcome/;
const matches = text.match(matchPattern);
console.log(`Matches for "welcome": ${matches ? matches[0] : 'No match found'}`);

Output

Index of "world": 22
Matches for "welcome": welcome

Conclusion

In this article, we have seen various methods for searching strings for a pattern. JavaScript has strong tools for searching strings and finding patterns in your applications. By picking the right method for what you need, you can easily search and work with text data in different situations.