📘 Day 6: Linear Search Algorithm in JavaScript

🔍 What is Linear Search?

Linear Search (also called sequential search) is the simplest search algorithm. It goes through each element of an array one by one until it finds the target value or reaches the end of the list.

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🧠 Real-life Analogy

Imagine you are looking for a friend's name in a guest list — so you start checking from the top and keep moving downward until you find it. That’s how linear search works!

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🛠️ How Linear Search Works

1. Start from the first element.

2. Compare it with the target.

3. If it matches, return the index.

4. If not, move to the next element.

5. If the target is not found till the end, return -1.

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💻 Code Example

javascriptCopyEditfunction linearSearch(arr, target) {
  for (let i = 0; i < arr.length; i++) {
    if (arr[i] === target) {
      return i; // Found, return index
    }
  }
  return -1; // Not found
}

// Example usage
const numbers = [10, 22, 5, 7, 90, 33];
const result = linearSearch(numbers, 90);

console.log(result); // Output: 4

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⏱️ Time & Space Complexity

💡 Best case is when the element is at the beginning of the array.

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⚖️ When Should You Use Linear Search?

• The list is unsorted.

• The list is short.

• You want simplicity over speed.

For larger, sorted datasets, binary search is much more efficient — and we’ll cover that soon 😉

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📚 Practice Questions

Here are 3 questions to reinforce today’s topic:

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✅ Easy: Find the Index of a Value

Write a function to find the index of 25 in this array:
[11, 13, 15, 25, 36]

Solution:

javascriptCopyEditfunction findIndex(arr, target) {
  for (let i = 0; i < arr.length; i++) {
    if (arr[i] === target) {
      return i;
    }
  }
  return -1;
}

console.log(findIndex([11, 13, 15, 25, 36], 25)); // Output: 3

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🧠 Intermediate: Search for a Name

Create a function that checks if the name "Alice" exists in a list of names. Return true or false.

Solution:

javascriptCopyEditfunction containsName(arr, name) {
  for (let i = 0; i < arr.length; i++) {
    if (arr[i] === name) {
      return true;
    }
  }
  return false;
}

console.log(containsName(["Bob", "Eve", "Alice", "Tom"], "Alice")); // Output: true

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🔥 Hard: Count How Many Times a Number Appears

Write a function that counts how many times 3 appears in the array:
[3, 1, 4, 3, 5, 3, 7]

Solution:

javascriptCopyEditfunction countOccurrences(arr, target) {
  let count = 0;
  for (let i = 0; i < arr.length; i++) {
    if (arr[i] === target) {
      count++;
    }
  }
  return count;
}

console.log(countOccurrences([3, 1, 4, 3, 5, 3, 7], 3)); // Output: 3

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🚀 Conclusion

Linear search is easy to implement and works well for small or unsorted lists. It's not the fastest, but it’s reliable and simple — a perfect start for every DSA learner.

📅 See you tomorrow for Day 7: Binary Search Algorithm — where things get faster and smarter 💡

#CodeWithGift #DSA2025 #JavaScript #DaySix