Find Pivot Index

LeetCode題目: 724. Find Pivot Index

My solution:

/**
 * @param {number[]} nums
 * @return {number}
 */
let pivotIndex = nums => {
    let leftBaseValue = 0;
    let rightBaseValue = nums.slice(0).reduce((prev,curr) => prev+curr, 0);
    for (let i=0; i<nums.length; i++) {
        leftBaseValue += nums[i-1] ?? 0;
        rightBaseValue -= nums[i];
        if(leftBaseValue === rightBaseValue) return i;
    }
    return -1;
};