A patch function in 67 bytes. It modifies a given object according to a diff as generated by this diff function.
For a full featured diff and patch library in 600 bytes check out dffptch.js.
See the 140byt.es site for a showcase of entries (built itself using 140-byte entries!), and follow @140bytes on Twitter.
To learn about byte-saving hacks for your own code, or to contribute what you've learned, head to the wiki.
140byt.es is brought to you by Jed Schmidt, with help from Alex Kloss. It was inspired by work from Thomas Fuchs and Dustin Diaz.
(a,b)=>{Object.assign(a,b.m);for(b in b.d)delete a[b]}