javascript - 以下程序是否在外循环的第一次迭代时执行嵌套循环？

Question

在嵌套循环的第一次迭代中 i = 2和 j = 2 .但是，嵌套循环的条件是 j < i .这是否意味着嵌套循环没有执行？发生了什么事？

showPrimes(10);

function showPrimes(n) {
    nextPrime:

    for (let i = 2; i < n; i++) {
        for (let j = 2; j < i; j++)
            if (i % j == 0) continue nextPrime;
        console.log(i); // a prime number
    }
}

Answer 1

这是一张详细说明程序流程的图表:

+---+---+-------------------------------------------------------------+
| i | j |                            Notes                            |
+---+---+-------------------------------------------------------------+
| 2 | 2 | Nested loop condition is false. Hence, 2 is a prime number. |
| 3 | 2 | 3 is not divisible by 2. Let's keep searching.              |
| 3 | 3 | Nested loop condition is false. Hence, 3 is a prime number. |
| 4 | 2 | 4 is divisible by 2. Hence, it's not a prime number.        |
| 5 | 2 | 5 is not divisible by 2. Let's keep searching.              |
| 5 | 3 | 5 is not divisible by 3. Let's keep searching.              |
| 5 | 4 | 5 is not divisible by 4. Let's keep searching.              |
| 5 | 5 | Nested loop condition is false. Hence, 5 is a prime number. |
| 6 | 2 | 6 is divisible by 2. Hence, it's not a prime number.        |
| 7 | 2 | 7 is not divisible by 2. Let's keep searching.              |
| 7 | 3 | 7 is not divisible by 3. Let's keep searching.              |
| 7 | 4 | 7 is not divisible by 4. Let's keep searching.              |
| 7 | 5 | 7 is not divisible by 5. Let's keep searching.              |
| 7 | 6 | 7 is not divisible by 6. Let's keep searching.              |
| 7 | 7 | Nested loop condition is false. Hence, 7 is a prime number. |
| 8 | 2 | 8 is divisible by 2. Hence, it's not a prime number.        |
| 9 | 2 | 9 is not divisible by 2. Let's keep searching.              |
| 9 | 3 | 9 is divisible by 3. Hence, it's not a prime number.        |
+---+---+-------------------------------------------------------------+

希望这能解释为什么即使在 i = 2 和 j = 2 时嵌套循环不执行，程序仍能运行。