javascript测试方法无法正常工作

Question

I have a conditional logic based on the OS version no. in the browser useragent string.

Here is the code i tried.

var useragent = "Linux; U; Android 2.2.1; en-gb; HTC_DesireZ_A7272 Build/FRG83D";

if((/2.3/).test(useragent)){
   alert("2");
}
else if((/3./).test(useragent)){
   alert("3");
}
else if((/4./).test(useragent)){
   alert("4");
}
else {
   alert("5");
}

I always get an alert with 3 .

I tried replacing test method with indexOf and i get an alert with 5 .

Can somebody explain why (/3./).test(useragent) returns true?

Answer 1

You always get this because your regex /3./ means - match 3 and any symbol behind it. You have to escape the . .

For example try /3\\./ , and respectively for the others: /2\\.3/ , /4\\./ .

Your code should look something like that:

var useragent = "Linux; U; Android 2.2.1; en-gb; HTC_DesireZ_A7272 Build/FRG83D";

if ((/Android 2\./).test(useragent)){
   alert("2");
} else if((/Android 3\./).test(useragent)){
   alert("3");
} else if((/Android 4\./).test(useragent)){
   alert("4");
} else {
   alert("5");
}