JavaScript 循环遍历所有带有标记名、警报的元素
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JavaScript loop through all elements with tagname, alert
提问by user43107
var all = document.getElementsByTagName("a");
for (var i=0, max=all.length; i < max; i++) {
alert(x.innerHTML);
}
The purpose of this script is obvious: it tries to loop through all the elements with the tag name a, and alert the contents of each one.
这个脚本的目的很明显：它试图遍历所有带有标签 name 的元素a，并提醒每个元素的内容。
It doesn't run right.
It works fine, with one element, it alerts it's contents, but when there are more then one, it starts echoing undefinedfor each.
它运行不正确。
它工作正常，只有一个元素，它会提醒它的内容，但是当有多个元素时，它开始undefined为每个元素回显。
采纳答案by uoryon
you should use alert(all[i].innerHTML). xis undefined
你应该使用alert(all[i].innerHTML). x未定义
回答by BenM
You haven't provided a definition for x. Try this:
您尚未提供x. 试试这个：
var all = document.getElementsByTagName("a");
for(var i = 0, max = all.length; i < max; i++)
{
alert(all[i].innerHTML);
}
回答by ZER0
xis obviously undefined. You need to have something like:
x显然是未定义的。你需要有这样的东西：
var all = document.getElementsByTagName("a");
for (var i = 0, x; x = all[i++];)
alert(x.innerHTML);
However alertin a loop is really annoying, I would suggest to use console.loginstead.
但是alert在循环中真的很烦人，我建议console.log改用。
Tips: in browsers that supports already for…of, such Firefox, you can simply have:
提示：在已经支持for...of 的浏览器中，比如 Firefox，你可以简单地拥有：
var all = document.getElementsByTagName("a");
for (var x of all)
console.log(x.innerHTML);
Of course you can't use that on webside across browsers, it's just something good to know in the upcoming ES6 – or if you're going to write a Firefox's extension for instance.
当然，你不能跨浏览器在 web 端使用它，在即将到来的 ES6 中了解它只是一件好事——或者如果你打算编写一个 Firefox 的扩展。
