Missing Number

LeetCode題目: 268. Missing Number

My solution:

/**
 * @param {number[]} nums
 * @return {number}
 */
let missingNumber = nums => {
    nums.sort((a, b) => a-b);
    for (let i=0; i<=nums.length; i++) {
        if(nums[i] !== i) return i;
    }
};