NickName:Liam W Ask DateTime:2013-09-15T00:33:47

Print Javascript in Javascript?

I am in the process of making an addon for a software that basically allows you to have 'responsive' adverts, by checking the page size with javascript and then outputting the relevant ad code to the screen.

This works fine for text ad codes, however I've hit a snag when the ad code is javascript - I can't get the user-provided javascript to output to the page and be executed.

Is this possible at all?

Here is some example code:

<div id="admanagerresponsive">
    <script type="text/javascript">
      adUnit = document.getElementById("admanagerresponsive");
      adWidth  = adUnit.offsetWidth;

      if (adWidth >= 728) {
        <output ad code>
      }
    </script>
</div>

The code above will be directly in the page.

Is such a thing possible?

EDIT:

could be any advertiser's code, such as adsense. It'll be user provided, and will be standard html. However, it could contain tags, and these will need to be rendered and outputted correctly...

Copyright Notice：Content Author:「Liam W」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/18803917/print-javascript-in-javascript

Answers

t.niese 2013-09-14T16:55:41

If you really need to inject add html code containing script tags and you are award of the security problems, i suggest to use a library like jQuery that takes care about the cross browser issues with executing <script> tags added later.\n\nAdditionally you need to take care about various pitfalls like:\nHtml paring is done before script parsing, so no matter where a </script> appears this will immediately end your script.\n\nThe examples are important for the situations where you have that code as inline script inside your html page.\n\nExample 1:\n\n<script>\n adUnit = document.getElementById(\"admanagerresponsive\");\n adWidth = adUnit.offsetWidth;if (adWidth >= 728) {\n // if you add </script> <b>this is visible as html</b> and everything below is not script anymore\n }\n</script>\n\n\nExample 2:\n\n<script>\n adUnit = document.getElementById(\"admanagerresponsive\");\n adWidth = adUnit.offsetWidth;if (adWidth >= 728) {\n var string = \"<script> var test;</script>\";//the same problem here everything behind the closing script tag is html and not script anymore\n }\n</script>\n\n\nSo if you need to have some script to inject there you need to make the </script> not to be detectable by the html parser:\n\n<script>\n adUnit = document.getElementById(\"admanagerresponsive\");\n adWidth = adUnit.offsetWidth;if (adWidth >= 728) {\n var string = \"<script> var test;</sc\"+\"ript>\";//that way the html parser does not detect the closing script tag\n }\n</script>\n\n\nA better solution is not to use inline script at all, not only for that reason, but because you should always keep css, js and html separated.",