The difference between document.styleSheets[0].rules and cssRules_javascript skills

I was using Firefox today and suddenly discovered a small problem. The former is used for IE and the latter is used for mozilla browser.

<style type="text/css"> a {color:red} </style>
[Ctrl A Select all Note: If you need to introduce external Js, you need to refresh to execute

]

And the counts of rules and cssRules The methods are also different! rules is the selector number; cssRules is the rule number. You can see this by running the following code using IE and firefox respectively.

<style type="text/css"> a,div,p {color:red} h5 {color:blue} </style>
[Ctrl A select all Note:

If you need to introduce external Js, you need to refresh to execute <script> if(document.styleSheets[0].cssRules){ alert(document.styleSheets[0].cssRules[0].style.cssText) }else{ alert(document.styleSheets[0].rules[0].style.cssText) } </script>]<script> if(document.styleSheets[0].cssRules){ alert(document.styleSheets[0].cssRules[1].selectorText+":"+document.styleSheets[0].cssRules[1].style.cssText) }else{ alert(document.styleSheets[0].rules[1].selectorText+":"+document.styleSheets[0].rules[1].style.cssText) } </script>