strStr in JavaScript

Introduction

strStr is a commonly used function in programming that is used to find the first occurrence of a target string (needle) within another string (haystack). In JavaScript, you can implement this function using various techniques and methods.

Syntax

The syntax for strStr function in JavaScript is as follows:

strStr(haystack, needle)

• haystack is the string within which we want to search for the needle.
• needle is the target string that we want to find within the haystack.

The function returns the index of the first occurrence of the needle within the haystack, or -1 if the needle is not found.

Implementation

Solution 1: Using indexOf()

One of the simplest ways to implement strStr function in JavaScript is by utilizing the indexOf() method, which is available for strings in JavaScript.

function strStr(haystack, needle) {
    return haystack.indexOf(needle);
}

// Usage
console.log(strStr('This is a test string', 'test')); // Output: 10
console.log(strStr('Hello, world!', 'foo')); // Output: -1

Solution 2: Brute Force Approach

Another approach to implement strStr function is by using a brute force method. In this method, we compare each character of the needle with the characters in the haystack one by one, starting from each index in the haystack.

function strStr(haystack, needle) {
    if (needle === '') return 0;
    for (let i = 0; i < haystack.length; i++) {
        let j;
        for (j = 0; j < needle.length; j++) {
            if (haystack[i + j] !== needle[j]) {
                break;
            }
        }
        if (j === needle.length) {
            return i;
        }
    }
    return -1;
}

// Usage
console.log(strStr('This is a test string', 'test')); // Output: 10
console.log(strStr('Hello, world!', 'foo')); // Output: -1

Solution 3: Using Regular Expression

JavaScript also provides the option to use regular expressions for pattern matching. We can employ a regular expression to find the needle within the haystack using the search() method.

function strStr(haystack, needle) {
    const pattern = new RegExp(needle);
    const result = haystack.search(pattern);
    return result;
}

// Usage
console.log(strStr('This is a test string', 'test')); // Output: 10
console.log(strStr('Hello, world!', 'foo')); // Output: -1

Conclusion

In this introduction, we explored different ways to implement the strStr function in JavaScript. Whether you choose to use built-in methods like indexOf() or prefer a more manual approach utilizing loops and comparisons, the goal remains the same - to find the first occurrence of a target string within another string. The choice of implementation depends on the specific requirements of your project or personal preference.