将JavaScript广告代码放置在页面中的其他位置

Question

I have a page, that calls "first.js" script. This script ads to a call to "second.js" script:

var head= document.getElementsByTagName('head')[0];
var script= document.createElement('script');
script.type= 'text/javascript';
script.src= 'second.js';
document.getElementsByTagName("head")[0].appendChild(script)

now, if I put in second.js alert("test"), I will see a good alert. However, if I put in second.js document.write("something"), I will not get that document.write.

Any idea why?

Answer 1

Because it is being loaded into the head , typically where none of the elements are rendered in the browser's viewport.

If this were to run too, it would clear the page if had started to render as document.write() implicitly calls document.open() first.