JavaScript: Missing number from an array

JavaScript Math: Exercise-83 with Solution

Find Missing Number in Array

Write a JavaScript program to find the missing number in a given array. There are no duplicates in the list.

Test Data:
([1,2,3,5,6,7]) -> 4
([2,3,4,5]) -> 1

Sample Solution:

JavaScript Code:

/**
 * Function to find the missing number in an array of consecutive integers.
 * @param {number[]} nums - The input array of consecutive integers.
 * @returns {number} - The missing number in the array.
 */
function test(nums) {
  // Iterate over consecutive integers up to the length of the input array + 1
  for (let n = 1; n <= nums.length + 1; n++) {
    // Check if the current integer is not found in the input array
    if (nums.indexOf(n) === -1) 
      // If the current integer is not found, return it as the missing number
      return n;
  }
}

// Test cases
// Assign value to nums
nums = [1, 2, 3, 5, 6, 7];
// Print the value of nums
console.log("nums = " + nums);
// Find the missing number in the said array
console.log("Missing number of the said array: " + test(nums));
// Repeat the above steps for a different value of nums
nums = [2, 3, 4, 5];
console.log("nums = " + nums);
console.log("Missing number of the said array: " + test(nums));

Output:

nums = 1,2,3,5,6,7
Missing number of the said array: 4
nums= 2,3,4,5
Missing number of the said array: 1

Flowchart:

Live Demo:

See the Pen javascript-math-exercise-83 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript function that finds the missing number in a consecutive sequence by using the arithmetic series sum formula.
• Write a JavaScript function that sorts an unsorted array of consecutive numbers and identifies the missing element.
• Write a JavaScript function that iterates through an array and detects gaps between consecutive numbers.
• Write a JavaScript function that uses the difference between expected and actual sums to determine the missing number.

Go to:

• JavaScript Math and Numbers Exercises Home ↩
• JavaScript Exercises Home ↩

PREV : Mean of Digits in a Number.
NEXT : Sum of Two Highest Numbers in Array.

Improve this sample solution and post your code through Disqus.