The comments are all in the code. It’s very detailed.
I only judged ie, Firefox and Google, because I didn’t install other browsers, so ha ha. Of course, if you want to judge other browsers. The basic code is the same.
//First of all, let’s take a look at what the three browsers have returned.
//ie ua=mozilla/4.0 (compatible; msie 8.0; windows nt 5.2; trident/4.0; qqpinyin 730; .net clr 1.1.4322)
//firefox ua=mozilla/5.0 (windows; u; windows nt 5.2; zh-cn; rv:1.9.2) gecko/20100115 firefox/3.6
//chrome ua=mozilla/5.0 (windows; u; windows nt 5.2; en-us) applewebkit/532.5 (khtml, like gecko) chrome/126.96.36.199 safari/532.5
//You can see the browser ie MSIE 8.0 firebox / 3.6 Chrome / 4.0.249 above
//We just need to use regular to find out which browser can match these key points in the string.
//Take a look at the regular expression of regular firebox / firebox \ / ([\ D \.] +)/
//Firebox \ / matches a character like firebox
//([[D \.] +) () indicates that the matching characters need to be captured. Later, you can use  to get the version number, which is his credit.
//It means to take the whole as a whole
//\D match a number. Match one. Add it together and you can match something like 8
//There’s a + on the outside of the  +]. He will repeat the original matching things in the , so it becomes 188.8.131.52. Of course, it can also be 48.1.563
//IE’s is basically the same as that of Firefox, there’s no big difference
//MSIE 8.0 is to match a space between MSIE and 8.0
//It’s the same as fox
//Only sys of the current browser can use  to return the version number
I have a problem. I saw the master write like this
Firebox \ / ([\ D.] +) / / expert’s
Firebox \ / ([\ D \.] +) / / my
//I wonder what the difference is between the two. I used a lot of STR tests. I don’t see any difference / / is it the same as [\ D.] +? Ask the master to answer.