Compatible writing method of addRule under firefox_javascript skills

There are really many ways to use scripts to control the style of html elements.
For a single element, you can directly use element.style.display=... to modify one style, or you can use element.className=... to modify its multiple styles.
To modify the styles of multiple elements, you can use scripts to directly import css files.
There is such a requirement in the current project. It is required to change the style of all descendant nodes under a certain div, but not change the style of the div itself.
I left the code without thinking:

Copy the code The code is as follows:

divdiv

spanspan

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<script> <br>function f(){ <br> var rule="#a1 *{background-color:red}"; <br> var index=document.styleSheets[0].cssRules.length; <br> document.styleSheets[0].insertRule(rule, index); <br>} <br></script>

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