Array Search JS

let input = [
    '1,1,1,1,1,1,1,1'
];

let print = this.print || console.log;
let gets = this.gets || ((arr, index) => () => arr[index++])(input, 0);

function solve() {
    let inputArr = gets().split(',').map(x => Number(x));
    const uniqueArrLength = inputArr.length;

    let array = [];
    for (let i = 1; i <= uniqueArrLength; i++) {
        array.push(i);
    }

    let uniqueArr = removeDuplicateElems(inputArr);

    for (const number of uniqueArr) {
        let index = array.indexOf(number);
        if(index !== -1) {
            array.splice(index, 1);
        }
    }

    const missingNums = array.join(',');

    print(missingNums);

    function removeDuplicateElems(arrArg) {
        let uniqueArr = [];
        for (let i = 0; i < arrArg.length; i++) {
            const num = arrArg[i];

            if(!uniqueArr.includes(num)) {
                uniqueArr.push(num);
            }
        }

        return uniqueArr;
    }
}

solve();