It will move all strings from the codes , to a single variable of the string table on the beginning of the code .
That will make the hacker more hard to get the relative data of each statements. And the implementation of Move Members require this feature.
For example , it's easy to read this code
o.style.color='red';
With this feature and Move Members, the code will look like as this
o[a[23]][a[52]]=a[145];