Flex String Splicing

Usually str+str2 is used directly when Flex String is spliced

Today I want to see if the functions that come with Flex are useful, and then use

str.concat(str2);

Alert.show(str);

The result did not change, and a fatal error was discovered. The concat function of flex did not change the data of the original String, but created a new String, which needs to be received.

change:

str= str.concat(str2);

Alert.show(str);

Everything is OK!