Missing digit JS in sword finger 0~n-1

A length of n-1 All numbers in the incremental sort array of are unique , And every number is in the range 0～n-1 within . In scope 0～n-1 Internal n There are and only one number is not in the array , Please find out the number .

Example 1:

Input : [0,1,3]
Output : 2
Example  2:

Input : [0,1,2,3,4,5,6,7,9]
Output : 8

/**
 * @param {number[]} nums
 * @return {number}
 */
var missingNumber = function(nums) {

    for(let i = 0;i<nums.length+1;i++){
        if(nums[i]!=i){
            return i
        }
        else if(nums.length===1){
            return 1
        }
    }
};