cobalt, in that example, blob is a constant.
changing the value of constants is not supported. that's what makes them constants. doing it anyway WILL result in 'undefined' behaviour. and by undefined, I mean 'predictable but horribly horribly buggy behaviour that can differ from one qcc to the next'.
DO NOT WRITE TO CONSTANTS.
add the var keyword if you want it to not be a constant.
any good qcc will warn about this.