stuff = promise( 'anything that might take a while' );

... do anything else that you can before you need the stuff
this = promise( 'read a file' );
that = promise( 'fetch something from a remote system' );
theOther = promise( 'query data from the DB' );

... perhaps check to see if stuff is available
if( !stuff->ready? ) doSomethingElse();

...
... if any of the four components isn't ready the statement blocks until it is.
... maybe  it needs a timeout either collectively or individually
... but that depends what else you might do at this point in the code; if anything.
combine( this, that, theOther, stuff );