Use Map object properly

[tiagoschenkel]

The bracket notation in JavaScript have a different behavior than the one expected in Action Script 3:

JS evaluates the first complete expression with square brackets in a statement, runs toString() on it to convert it into a string and then uses that value for the next bracket expression, on down the line till it runs out of bracket expressions.

Reference: JS dot-notation vs. bracket notation

To avoid problems with the collision of keys, a Map object must be manipulated using all available methods provided by the official implementation instead.

See Map.