Javascript 检查数组的元素

Question

如果一个数组的元素除一个为 1 之外全为 0，我如何检查它？

示例:

array = [0, 0, 0, 1, 0];
check(array); //returns the index where it is 1 which is 3

array = [0, 3, 0, 2, 0];
check(array); //returns -1

array = [0, 3, 1, 2, 0];
check(array); //returns -1 again if there are non zero aside from 1, it should be one 1 and others are all 0.

array = [0, 0, 1, 0, 1];
check(array); //returns -1 again, there should just be one element of 1

Answer 1

function check(a) {
    var index = -1;
    for (var i = 0; i < a.length; i++) {
        if (a[i] == 1) {
            if (index < 0) {
                index = i;
            } else {
                return -1;
            }
        } else if (a[i] != 0) {
            return -1;
        }
    }
    return index;
}

array1 = [0, 0, 0, 1, 0];
check(array1); //returns 3

array2 = [0, 3, 0, 2, 0];
check(array2); //returns -1