function foo() {
return Math.random() < 0.5;
}

function foo2() {
for (;;) {
let n = 0;
for (let i = 0; i < 4; ++i) {
n *= 2;
if (foo()) {
n += 1;
}
}
if (n <= 9) {
return n;
}
}
}

!function foo2_test(times) {
let res = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, ];

for (var i = 0; i < times; i++) {
res[foo2()] += 1;
}

for (let i = 0; i < res.length; ++i) {
console.log(times + "次调用中" + i + "的次数： " + res[i]);
}
} (10000);