DCP4 - Missing integer

function findMissingInt(arr){
    i = 0;
    while(arr.indexOf(i) != -1){
        // If index is not -1, it will be another number, it means that this number eixsts
        i++;
    }
    return i;
}

// MAIN FUNCTION
arr1 = [1, 2, 3, 7, 0];
arr2 = [0, -1, -2, 3];
arr3 = [-1, -2, -5]
arr4 = [0, 3, 1, -9, 10, 2, 4, 6, 7, 5, 5]
console.log();
console.log(arr1 + " ----> missing int = " + findMissingInt(arr1));
console.log(arr2 + " ----> missing int = " + findMissingInt(arr2));
console.log(arr3 + " ----> missing int = " + findMissingInt(arr3));
console.log(arr4 + " ----> missing int = " + findMissingInt(arr4));