Implement Linear Search Algorithm in JavaScript

Objective:

• Implement a linear search function that searches for a given target in an array and returns its index or -1 if the target is not present.

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Requirements:

1. Write a function linearSearch(arr, target) that:
   • Accepts an array arr and a target value.
   • Returns the index of the target if found.
   • Returns -1 if the target is not found in the array.
2. The algorithm should check each element of the array one by one, making it a linear search with a time complexity of O(n).

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Steps:

1. Function Definition:

   • Define the function linearSearch(arr, target).

2. Iterate Over the Array:

   • Use a for loop to iterate over each element in the array.
   • During each iteration, compare the current element with the target value.

3. Return the Index:

   • If the current element matches the target, return its index.
   • If the loop finishes and no match is found, return -1.

4. Edge Cases:

   • Handle cases where the array is empty by returning -1.
   • Test with an array containing multiple occurrences of the target and return the first match.
   • Ensure the function works with both numeric and string arrays.

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Resources:

• Linear Search Algorithm
• JavaScript Array Methods

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Solution:

Here’s the solution for the linear search implementation in JavaScript:

// Linear search function
function linearSearch(arr, target) {
  // Iterate over each element in the array
  for (let i = 0; i < arr.length; i++) {
    // If the current element matches the target, return the index
    if (arr[i] === target) {
      return i;
    }
  }
  // If target is not found, return -1
  return -1;
}

// Example Usage
const array = [10, 23, 45, 70, 34, 50];
const target = 45;

console.log(linearSearch(array, target)); // Output: 2
console.log(linearSearch(array, 100));    // Output: -1

Explanation:

linearSearch():

• The function takes two parameters: an array arr and a target value.
• It uses a for loop to iterate through each element in the array.
• When it finds an element equal to the target value, it returns the current index.
• If the loop finishes and the target is not found, it returns -1.

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Edge Cases:

• If the array is empty, the function immediately returns -1.
• If the target is not present in the array, the function returns -1.
• If there are multiple occurrences of the target, the function returns the index of the first occurrence.

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Time Complexity:

• The time complexity of the linear search algorithm is O(n), where n is the number of elements in the array. This is because, in the worst case, every element must be checked once.