请解释此javaScript代码如何删除所有节点 HTML

阅读

HTML

while(myList.firstChild) {
    myList.removeChild(myList.firstChild)
};

1st time while loop run firstChild is <li>Item 1</li> --> code runs and remove it.

2nd time while loop run firstChild is <li>Item 2</li> --> code runs and remove it.

3rd time while loop run firstChild is <li>Item 3</li> --> code runs and remove it.

4th time while loop run firstChild is <li>Item 4</li> --> code runs and remove it.

运行时

while(myList.firstChild) // loop will run while myList has a firstChild
    {myList.removeChild(myList.firstChild)
};

第一次循环运行时，第一个子项是
项1
-->代码运行并将其删除。

现在使用HTML

while(myList.firstChild) {
    myList.removeChild(myList.firstChild)
};

1st time while loop run firstChild is <li>Item 1</li> --> code runs and remove it.

2nd time while loop run firstChild is <li>Item 2</li> --> code runs and remove it.

3rd time while loop run firstChild is <li>Item 3</li> --> code runs and remove it.

4th time while loop run firstChild is <li>Item 4</li> --> code runs and remove it.

项目2
项目3
项目4

跑

第二次，循环运行firstChild是
项2
-->代码运行并删除它。

现在使用HTML

while(myList.firstChild) {
    myList.removeChild(myList.firstChild)
};

1st time while loop run firstChild is <li>Item 1</li> --> code runs and remove it.

2nd time while loop run firstChild is <li>Item 2</li> --> code runs and remove it.

3rd time while loop run firstChild is <li>Item 3</li> --> code runs and remove it.

4th time while loop run firstChild is <li>Item 4</li> --> code runs and remove it.

项目3
项目4

跑

当循环运行firstChild是第3项时，

3次运行并删除它。

现在使用HTML

while(myList.firstChild) {
    myList.removeChild(myList.firstChild)
};

1st time while loop run firstChild is <li>Item 1</li> --> code runs and remove it.

2nd time while loop run firstChild is <li>Item 2</li> --> code runs and remove it.

3rd time while loop run firstChild is <li>Item 3</li> --> code runs and remove it.

4th time while loop run firstChild is <li>Item 4</li> --> code runs and remove it.

项目4

跑

第四次，循环运行firstChild是
项4
-->代码运行并删除它。

现在使用HTML

while(myList.firstChild) {
    myList.removeChild(myList.firstChild)
};

1st time while loop run firstChild is <li>Item 1</li> --> code runs and remove it.

2nd time while loop run firstChild is <li>Item 2</li> --> code runs and remove it.

3rd time while loop run firstChild is <li>Item 3</li> --> code runs and remove it.

4th time while loop run firstChild is <li>Item 4</li> --> code runs and remove it.

跑

---

js代码不会运行，因为在

myList

中没有第一个子项。While循环条件失败。

它是这样工作的，While循环将一直执行，直到

myList

有第一个子项为止。在循环中，你移除每个第一个孩子，这样下一个就成为第一个孩子。当

myList.firstChild

变为空时，它将继续执行，直到所有内容都被删除为止。它是

falsy

，因此不再运行循环。这很有帮助。循环将删除节点的第一个子节点–

removeChild

–myList.firstChild，直到该节点不再有第一个子节点（因此也不再有子节点）。