Get the file Suffix in Javascript

VaR STRF = Filename. substr (filename. Length - 4 , 4 ); // Get the file suffix (the last four character strings in the string)

String. substr (N1, N2) is a string that is commonly used to extract the specified length (N2) from the specified position (N1;
String. substring (N1, N2) is a little special. It first finds a small value from N1, N2, and then starts from the starting position of the string, intercept a string between a smaller value position and a smaller value. The length of the truncated string is the difference between a smaller value and a smaller value.