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<title>Title</title>
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<div id="#12">我喜欢学习python</div>
<a>123</a>
<a>456</a>
<a>789</a>
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document.getElementById('#12')
<div id="#12">我喜欢学习python</div>
document.getElementById('#12').innerText
"我喜欢学习python"
document.getElementById('#12').innerText="我也超级喜欢"
"我也超级喜欢"
document.getElementsByTagName('a')[1]
<a>456</a>
document.getElementsByTagName('a')[1].innerText='qwe'
"qwe"
msg = document.getElementsByTagName('a')
HTMLCollection(3) [a, a, a]
for(var i=0;i<msg;i++){msg[i].innerText=111}
undefined
for(var i=0;i<msg;i++){msg[i].innerText=111;}
undefined
for(var i=0;i<msg.length;i++){msg[i].innerText=111}
111