为什么javascript没有加载document.readyState ===" complete"

问题描述：

我刚开始从 w3school 学习javascript，我找到了out你只能在HTML输出中使用document.write。如果在文档加载后使用它，整个文档将被覆盖。所以我试着写下面的代码来检查有效性：

I have just started learning javascript from w3school and I have found out that "You can only use document.write in the HTML output. If you use it after the document has loaded, the whole document will be overwritten." so I have tried to write following code to check the validity:

<html>
    <head>
        <title>ashish javascript learning</title>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    </head>
    <body>
        <p> sample html with javascript </p>
        <script>
            document.write("<h1>this is heading</h1>");
            document.write("<p>this is sample para</p>");
        </script>
        <script>
            if(document.readyState === "complete"){
                loaded();
            }
            function loaded(){
                document.write("<p>loading content after the document has been loaded");
            }
        </script>
    </body>
</html>

代码仍然显示旧值，并且不会覆盖网页内容。你能告诉我我做错了什么吗？

Code is still showing the old value and is not overwriting the content of the web page. Could you suggest me what am I doing wrongly.

答

当你正在测试 document.readyState ===complete，文件的readyState 不是完成，它是加载，所以没有任何反应，并且从未调用已加载。

At the time you're testing document.readyState === "complete", the document's readyState isn't "complete", it "loading", so nothing happens, and loaded is never called.

您可以侦听readyState进行更改，然后检查它是否完整（或收听 window.onload 这更容易）：

You can listen for the readyState to change, and then check to see if it is "complete" (or listen to window.onload which is easier):

document.onreadystatechange = function () {
  if(document.readyState === "complete"){
    loaded();
  }
}

为什么javascript没有加载document.readyState ===" complete"

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