[z3t4]

By helping out the compiler you can get better performance. But I like to think that current JavaScript engines or future ones are quite smart and can optimize beyond that.

Lets say you are writing software for a cargo company ... The code has well defined classes. The company now wants to expend by including buss goods. But in the code, the terminals and containers will only accept trucks ... It would be better if the terminal code checked if the good fitted etc.

Thinking about Buss vs Truck is much better then thinking about Array vs Object, but you shouldn't let classifications limit the solutions either.