nsACString string1("Hello"); nsACString string2(" world!"); string1.Append(string2);
nsACString string1("The quick brown "); nsACString string2("fox jumps over the lazy dog."); nsACString string3(" 1234567890"); string1.Append(string2); string1.Append(string3, 5, 5);In this example, `string2` and a substring of `string3` (from index 5 to the next 5 characters) are appended to `string1`, resulting in the value "The quick brown fox jumps over the lazy dog.56789". This function is useful when creating or manipulating strings within Mozilla-based applications.