JavaScript: Find the number of even values in sequence before the first occurrence of a given number

JavaScript Basic: Exercise-110 with Solution

Count Evens Before First Occurrence of Number

Write a JavaScript program to find the number of even values in sequence before the first occurrence of a given number.

Sample sequence = [1,2,3,4,5,6,7,8]
Given number: 5
Output: 2

Sample Solution:

JavaScript Code:

// Function to count even numbers before the given number in the array
function find_numbers(arr_num, num) {
    var result = 0; // Counter variable to store the count of even numbers
    for (var i = 0; i < arr_num.length; i++) {
        if (arr_num[i] % 2 === 0 && arr_num[i] !== num) { // Check if number is even and not equal to 'num'
            result++; // Increment the counter for each even number
        }
        if (arr_num[i] === num) { // Check if the current number matches 'num'
            return result; // Return the count of even numbers encountered so far
        }
    }
    return -1; // Return -1 if 'num' is not found in the array
}

// Example usage of the function
console.log(find_numbers([1, 2, 3, 4, 5, 6, 7, 8], 5));  
console.log(find_numbers([1, 3, 5, 6, 7, 8], 6)); 

Output:

2
0

Live Demo:

See the Pen javascript-basic-exercise-110 by w3resource (@w3resource) on CodePen.

Flowchart:

ES6 Version:

// Function to find numbers in an array that are even and not equal to a specific number
const find_numbers = (arr_num, num) => {
  let result = 0; // Initialize the count of even numbers not equal to 'num'

  for (let i = 0; i < arr_num.length; i++) {
    if (arr_num[i] % 2 === 0 && arr_num[i] !== num) {
      result++; // Increment count for even numbers not equal to 'num'
    }
    if (arr_num[i] === num) {
      return result; // Return the count when 'num' is found in the array
    }
  }

  return -1; // Return -1 if 'num' is not found in the array
};

// Example usage of the function
console.log(find_numbers([1, 2, 3, 4, 5, 6, 7, 8], 5)); // Output: 2 (even numbers not equal to 5: 2, 4)
console.log(find_numbers([1, 3, 5, 6, 7, 8], 6)); // Output: -1 (6 not found in the array)

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