solution.js

const decreaseEven = (nums) => {
 let count = 0
 for (let i = 0; i < nums.length; i = i + 2) {
 if (i === 0) {
 if (nums[0] >= nums[1]) {
 count += (nums[0] - nums[1] + 1)
 }

 continue
 }

 if (i === nums.length - 1) {
 const lastIndex = nums.length - 1
 if (nums[lastIndex] >= nums[lastIndex - 1]) {
 count += (nums[lastIndex] - nums[lastIndex - 1] + 1)
 }

 continue
 }

 const target = (nums[i - 1] < nums[i + 1])
 ? nums[i - 1]
 : nums[i + 1]

 if (nums[i] >= target) {
 count += (nums[i] - target + 1)
 }
 }

 return count
}

const decreaseOdd = (nums) => {
 let count = 0
 for (let i = 1; i < nums.length; i = i + 2) {
 if (i === nums.length - 1) {
 const lastIndex = nums.length - 1
 if (nums[lastIndex] >= nums[lastIndex - 1]) {
 count += (nums[lastIndex] - nums[lastIndex - 1] + 1)
 }

 continue
 }

 const target = (nums[i - 1] < nums[i + 1])
 ? nums[i - 1]
 : nums[i + 1]

 if (nums[i] >= target) {
 count += (nums[i] - target + 1)
 }
 }

 return count
}

const movesToMakeZigzag = (nums) => {
 const countEven = decreaseEven(nums)
 const countOdd = decreaseOdd(nums)

 return Math.min(countEven, countOdd)
}

module.exports = movesToMakeZigzag