Why regExp test with flag 'g' return wrong value?

Question

The test function of the regular expression returns an invalid value when the 'g' flag is present.

Example:

var regExpArh = /(\.rar|\.zip|\.7z)$/gi;
var s = "55.7z";
regExpArh.test(s); // return true
regExpArh.test(s); // return false
regExpArh.test(s); // return true
regExpArh.test(s); // return false

Why?

Answer 1

See this documentation.

If the regex has the global flag set, test() will advance the lastIndex of the regex. A subsequent use of test() will start the search at the substring of str specified by lastIndex (exec() will also advance the lastIndex property).