问题
I just tried this code on my browser (Chrome 39, Windows 8) :-
<html>
<body>
<script>
<!--
document.write("<h1>Hello</h1>");
-->
</script>
</body>
</html>
This produces the Header text on the browser. But when I make a slight change- put the HTML comment stuff on a single line,
<html>
<body>
<script>
<!-- document.write("<h1>Hello</h1>"); -->
</script>
</body>
</html>
This doesn't display anything. Why is it so? I don't think HTML comments are in the Javascript standards.
p.s. I know how to put javascript comments. I'm only wondering about this erratic behavior.
回答1:
That's the way to hide javascript to browsers that don't recognize the script element. The first line is allways ignored: Hiding script data from user agents
Commenting scripts in JavaScript
The JavaScript engine allows the string
"<!--"to occur at the start of aSCRIPTelement, and ignores further characters until the end of the line. JavaScript interprets"//"as starting a comment extending to the end of the current line. This is needed to hide the string"-->"from the JavaScript parser.<SCRIPT type="text/javascript"> <!-- to hide script contents from old browsers function square(i) { document.write("The call passed ", i ," to the function.","<BR>") return i * i } document.write("The function returned ",square(5),".") // end hiding contents from old browsers --> </SCRIPT>
来源：https://stackoverflow.com/questions/27428277/why-does-javascript-ignore-single-line-html-comments