</p> <div id="doc">123</div> <p><script></p> <p> var main = document.getElementById('doc');</p> <p> var output1 = main.childNodes.length;</p> <p> var textNode1 = document.createTextNode('This is some text.');</p> <p> var textNode2 = document.createTextNode('This is another text.');</p> <p> main.appendChild(textNode1);</p> <p> main.appendChild(textNode2);</p> <p> var output2 = main.childNodes.length;</p> <p> alert(output2)</p> <p> main.normalize();</p> <p> var output3 = main.childNodes.length;</p> <p> alert(output3)</p> <p></script></p> <p> [Ctrl+A 全部选择 提示：你可先修改部分代码，再按运行]