ActionScript: The Definitive Guide

The String Operators

Special string operators—concatenation (&), equality (eq ), inequality (ne), and comparison (lt, gt, le, ge)—were required when using string data in Flash 4. In Flash 5 and later, the special string operators are deprecated (i.e., supported but obsolete). Use ==, !=, <, >, <=, and >= for string comparisons, unless exporting to Flash 4 .swf format, in which case you must use the old operators (eq , ne, lt, gt, le, ge). Use + for string concatenation, unless exporting to Flash 4 format, in which case you should use add instead of & (because & is the bitwise AND operator in Flash 5 and later).

For more details and a list of Flash 4 versus Flash 5 string-operation equivalencies, see Section 4.6 and Table 4.2 in Chapter 4.