javascript - Document.write clears page

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javascript - Document.write clears page

posted Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

javascript - Document.write clears page

Why in the code below upon the call of document.write in the function validator() the form elements (the checkbox and button) are removed from screen?

<!DOCTYPE html>
<html>
    <head>
        <script type="text/javascript">
            function validator() {
                if (document.myForm.thebox.checked)
                    document.write("checkBox is checked");
                else 
                    document.write("checkBox is NOT checked");
            }
        </script>
    </head>
    <body>
        <form name="myForm">
            <input type="checkbox" name ="thebox"/>
            <input type="button" onClick="validator()" name="validation" value="Press me for validation"/>
        </form>
    </body>
</html>

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1 Reply

深蓝 · Answer 1 · 2021-10-16T22:29:05+0000

document.write() is used to write to the document stream.

In your case, the stream is most probably already closed when the onClick handler is called, because your document has finished loading.

Calling document.write() on a closed document stream automatically calls document.open(), which will clear the document.

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